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/builtin/pty.c

@@ -125,9 +125,10 @@ static const char usage[] =
 #define CMIN		1
 #endif
 
-static void outofmemory(void)
+static noreturn void outofmemory(void)
 {
 	error(ERROR_SYSTEM|ERROR_PANIC, "out of memory");
+	UNREACHABLE();
 }
 
 #if !_lib_openpty && !_lib__getpty && !defined(_pty_clone)
@@ -221,7 +222,6 @@ static int
 mkpty(int* master, int* minion)
 {
 	struct termios	tty;
-	struct termios	tst;
 	struct termios*	ttyp;
 #ifdef TIOCGWINSZ
 	struct winsize	win;
@@ -316,6 +316,7 @@ mkpty(int* master, int* minion)
 		return -1;
 #endif
 #ifdef I_PUSH
+	struct termios	tst;
 	if (tcgetattr(*minion, &tst) < 0 && (ioctl(*minion, I_PUSH, "ptem") < 0 || ioctl(*minion, I_PUSH, "ldterm") < 0))
 	{
 		close(*minion);
@@ -1057,17 +1058,26 @@ b_pty(int argc, char** argv, Shbltin_t* context)
 			break;
 		case '?':
 			error(ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 		}
 		break;
 	}
 	argv += opt_info.index;
 	if (!argv[0])
+	{
 		error(ERROR_exit(1), "command must be specified");
+		UNREACHABLE();
+	}
 	if (mkpty(&master, &minion) < 0)
+	{
 		error(ERROR_system(1), "unable to create pty");
+		UNREACHABLE();
+	}
 	if (!(mp = sfnew(NiL, 0, SF_UNBOUND, master, SF_READ|SF_WRITE)))
+	{
 		error(ERROR_system(1), "cannot open master stream");
+		UNREACHABLE();
+	}
 	if (stty)
 	{
 		n = 2;
@@ -1095,9 +1105,15 @@ b_pty(int argc, char** argv, Shbltin_t* context)
 	if (!log)
 		lp = 0;
 	else if (!(lp = sfopen(NiL, log, "w")))
+	{
 		error(ERROR_system(1), "%s: cannot write", log);
+		UNREACHABLE();
+	}
 	if (!(proc = runcmd(argv, minion, session)))
+	{
 		error(ERROR_system(1), "unable run %s", argv[0]);
+		UNREACHABLE();
+	}
 	close(minion);
 	if (messages)
 	{
@@ -1109,7 +1125,10 @@ b_pty(int argc, char** argv, Shbltin_t* context)
 		else if ((fd = open(messages, O_CREAT|O_WRONLY, MODE_666)) >= 0)
 			drop = 0;
 		else
+		{
 			error(ERROR_system(1), "%s: cannot redirect messages", messages);
+			UNREACHABLE();
+		}
 		close(2);
 		dup(fd);
 		if (drop)
@@ -1118,6 +1137,9 @@ b_pty(int argc, char** argv, Shbltin_t* context)
 	minion = (*fun)(mp, lp, delay, timeout);
 	master = procclose(proc);
 	if (lp && sfclose(lp))
+	{
 		error(ERROR_system(1), "%s: write error", log);
+		UNREACHABLE();
+	}
 	return minion ? minion : master;
 }