Fix more compiler warnings, typos and other minor issues (#260)

Many of these changes are minor typo fixes. The other changes
(which are mostly compiler warning fixes) are:

NEWS:
- The --globcasedetect shell option works on older Linux kernels
  when used with FAT32/VFAT file systems, so remove the note about
  it only working with 5.2+ kernels.

src/cmd/ksh93/COMPATIBILITY:
- Update the documentation on function scoping with an addition
  from ksh93v- (this does apply to ksh93u+).

src/cmd/ksh93/edit/emacs.c:
- Check for '_AST_ksh_release', not 'AST_ksh_release'.

src/cmd/INIT/mamake.c,
src/cmd/INIT/ratz.c,
src/cmd/INIT/release.c,
src/cmd/builtin/pty.c:
- Add more uses of UNREACHABLE() and noreturn, this time for the
  build system and pty.

src/cmd/builtin/pty.c,
src/cmd/builtin/array.c,
src/cmd/ksh93/sh/name.c,
src/cmd/ksh93/sh/nvtype.c,
src/cmd/ksh93/sh/suid_exec.c:
- Fix six -Wunused-variable warnings (the name.c nv_arrayptr()
  fixes are also in ksh93v-).
- Remove the unused 'tableval' function to fix a -Wunused-function
  warning.

src/cmd/ksh93/sh/lex.c:
- Remove unused 'SHOPT_DOS' code, which isn't enabled anywhere.
  https://github.com/att/ast/issues/272#issuecomment-354363112

src/cmd/ksh93/bltins/misc.c,
src/cmd/ksh93/bltins/trap.c,
src/cmd/ksh93/bltins/typeset.c:
- Add dictionary generator function declarations for former
  aliases that are now builtins (re: 1fbbeaa1, ef1621c1, 3ba4900e).
- For consistency with the rest of the codebase, use '(void)'
  instead of '()' for print_cpu_times.

src/cmd/ksh93/sh/init.c,
src/lib/libast/path/pathshell.c:
- Move the otherwise unused EXE macro to pathshell() and only
  search for 'sh.exe' on Windows.

src/cmd/ksh93/sh/xec.c,
src/lib/libast/include/ast.h:
- Add an empty definition for inline when compiling with C89.
  This allows the timeval_to_double() function to be inlined.

src/cmd/ksh93/include/shlex.h:
- Remove the unused 'PIPESYM2' macro.

src/cmd/ksh93/tests/pty.sh:
- Add '# err_exit #' to count the regression test added in
  commit 113a9392.

src/lib/libast/disc/sfdcdio.c:
- Move diordwr, dioread, diowrite and dioexcept behind
  '#ifdef F_DIOINFO' to fix one -Wunused-variable warning and
  multiple -Wunused-function warnings (sfdcdio() only uses these
  functions when F_DIOINFO is defined).

src/lib/libast/string/fmtdev.c:
- Fix two -Wimplicit-function-declaration warnings on Linux by
  including sys/sysmacros.h in fmtdev().

src/cmd/INIT/RELEASE

@@ -423,7 +423,7 @@
 03-09-23 ratz.c: fix tar header number parse bug that skipped to next number
 	 regress.sh: rm cleanup now handles files matching -*
 03-09-11 iffe.sh: add unnamed { ... } blocks
-	 regress.sh: add COPY from to, like MOVE but comprison still done
+	 regress.sh: add COPY from to, like MOVE but comparison still done
 	 regress.sh: rm -rfu to handle test dirs w/o u+rwx
 03-08-14 Makefile: add hello.c to the manifest
 03-08-11 package.sh: fix `html binary' generation
@@ -522,7 +522,7 @@
 	 make.probe: add CC.LD.STRIP for link time a.out strip
 	 package.sh: fix package_use vs. PACKAGE_USE check
 02-10-24 WWW.mk: fix bug that required a :WWWBIN: assertion to post
-02-10-23 mamake.c: fix unuinitialized time in make()
+02-10-23 mamake.c: fix uninitialized time in make()
 	 ratz.c: fix meter buffer overflow
 02-10-20 package.sh: fix lib/probe/C/make/probe update test
 02-10-18 probe.win32: update for mingw
@@ -604,7 +604,7 @@
 	 package.sh: add check for { cc ar nm yacc/bison } before make
 	 ratz.c: fix "rb" vs. "r" macro tests
 	 iffe.sh: add nxt, similar to lcl but defines _nxt_foo for #include
-	 iffe.sh,package.sh: remove vaibale from sccs,cvs ident strings -- duh
+	 iffe.sh,package.sh: remove variable from sccs,cvs ident strings -- duh
 02-01-24 C+probe: check CC.DYNAMIC to handle cc that accept but ignore -B*
 	 iffe.sh: handle 'mem struct.a.b'
 02-01-22 iffe.sh: cache (internal) `foo vs. struct foo' test results
@@ -855,7 +855,7 @@
 98-05-01 regress: fix bug sometimes didn't list last test
 98-04-01 hostinfo: add cc path arg
 	 hostinfo: now works with /bin/sh
-	 Makefile: strengthed -lm probe
+	 Makefile: strengthen -lm probe
 98-01-23 Makefile: check for -ldl -lm
 	 C.probe: handle gcc -v -E phony include dirs
 	 iffe: fix lcl by dropping sort -u -- we need the real first

src/cmd/INIT/mamake.c

@@ -2157,8 +2157,8 @@ main(int argc, char** argv)
 			search(state.vars, "-strip-symbols", "1");
 			continue;
 		case '?':
-			error(ERROR_USAGE|4, "%s", opt_info.arg);
-			continue;
+			error(ERROR_usage(2), "%s", opt_info.arg);
+			UNREACHABLE();
 		case ':':
 			error(2, "%s", opt_info.arg);
 			continue;
@@ -2166,7 +2166,10 @@ main(int argc, char** argv)
 		break;
 	}
 	if (error_info.errors)
-		error(ERROR_USAGE|4, "%s", optusage(NiL));
+	{
+		error(ERROR_usage(2), "%s", optusage(NiL));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 #else
 	while ((s = *++argv) && *s == '-')

src/cmd/INIT/ratz.c

@@ -426,8 +426,8 @@ typedef uLong FAR uLongf;
 #  define z_off_t off_t
 #endif
 #ifndef SEEK_SET
-#  define SEEK_SET        0       /* Seek from beginning of file.  */
-#  define SEEK_CUR        1       /* Seek from current position.  */
+#  define SEEK_SET        0       /* Seek from beginning of file. */
+#  define SEEK_CUR        1       /* Seek from current position. */
 #  define SEEK_END        2       /* Set file pointer to EOF plus "offset" */
 #endif
 #ifndef z_off_t
@@ -1391,7 +1391,7 @@ typedef struct internal_state {
      */
 
     int level;    /* compression level (1..9) */
-    int strategy; /* favor or force Huffman coding*/
+    int strategy; /* favor or force Huffman coding */
 
     uInt good_match;
     /* Use a faster search when the previous match is longer than this */
@@ -2087,7 +2087,7 @@ unsigned start;         /* inflate()'s starting value for strm->avail_out */
     unsigned dmask;             /* mask for first level of distance codes */
     code this;                  /* retrieved table entry */
     unsigned op;                /* code bits, operation, extra bits, or */
-                                /*  window position, window bytes to copy */
+                                /* window position, window bytes to copy */
     unsigned len;               /* match length, unused bytes */
     unsigned dist;              /* match distance */
     unsigned char FAR *from;    /* where to copy match from */
@@ -4813,8 +4813,8 @@ char**	argv;
 			sfprintf(sfstdout, "%s\n", id + 10);
 			return 0;
 		case '?':
-			error(ERROR_USAGE|4, "%s", opt_info.arg);
-			continue;
+			error(ERROR_usage(2), "%s", opt_info.arg);
+			UNREACHABLE();
 		case ':':
 			error(2, "%s", opt_info.arg);
 			continue;
@@ -4822,7 +4822,10 @@ char**	argv;
 		break;
 	}
 	if (error_info.errors)
-		error(ERROR_USAGE|4, "%s", optusage(NiL));
+	{
+		error(ERROR_usage(2), "%s", optusage(NiL));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 #else
 	while ((s = *++argv) && *s == '-' && *(s + 1))

src/cmd/INIT/release.c

@@ -238,8 +238,8 @@ main(int argc, char** argv)
 			sfprintf(sfstdout, "%s\n", id + 10);
 			return 0;
 		case '?':
-			error(ERROR_USAGE|4, "%s", opt_info.arg);
-			continue;
+			error(ERROR_usage(2), "%s", opt_info.arg);
+			UNREACHABLE();
 		case ':':
 			error(2, "%s", opt_info.arg);
 			continue;
@@ -247,7 +247,10 @@ main(int argc, char** argv)
 		break;
 	}
 	if (error_info.errors)
-		error(ERROR_USAGE|4, "%s", optusage(NiL));
+	{
+		error(ERROR_usage(2), "%s", optusage(NiL));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 #else
 	while ((s = *++argv) && *s == '-' && *(s + 1))