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/lib/libast/disc/sfdcdio.c

@@ -42,6 +42,8 @@ typedef struct _direct_s
 /* convert a pointer to an int */
 #define P2I(p)	(Sfulong_t)((char*)(p) - (char*)0)
 
+#ifdef F_DIOINFO
+
 #if __STD_C
 static ssize_t diordwr(Sfio_t* f, Void_t* buf, size_t n, Direct_t* di, int type)
 #else
@@ -59,7 +61,6 @@ int		type;
 	done = 0;	/* amount processed by direct IO */
 	rv = 0;
 
-#ifdef F_DIOINFO
 	if((P2I(buf)%di->dio.d_mem) == 0 &&
 	   (f->here%di->dio.d_miniosz) == 0 && n >= di->dio.d_miniosz )
 	{	/* direct IO ok, make sure we're in the right mode */
@@ -92,7 +93,6 @@ int		type;
 		di->cntl &= ~FDIRECT;
 		(void)fcntl(f->file, F_SETFL, di->cntl);
 	}
-#endif /*F_DIOINFO*/
 
 	if((rw = n-done) > 0 &&
 	   (rv = type == SF_READ ? read(f->file,buf,rw) : write(f->file,buf,rw)) > 0 )
@@ -141,18 +141,18 @@ Sfdisc_t*	disc;
 
 	if(type == SF_FINAL || type == SF_DPOP)
 	{
-#ifdef F_DIOINFO
 		if(di->cntl&FDIRECT)
 		{	di->cntl &= ~FDIRECT;
 			(void)fcntl(f->file,F_SETFL,di->cntl);
 		}
-#endif
 		free(disc);
 	}
 
 	return 0;
 }
 
+#endif /* F_DIOINFO */
+
 #if __STD_C
 int sfdcdio(Sfio_t* f, size_t bufsize)
 #else