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/ksh93/include/defs.h

@@ -81,7 +81,7 @@ struct sh_scoped
 	char		*funname;
 	int		lineno;
 	Dt_t		*save_tree;	/* var_tree for calling function */
-	struct sh_scoped *self;		/* pointer to copy of this scope*/
+	struct sh_scoped *self;		/* pointer to copy of this scope */
 	Dt_t		*var_local;	/* local level variables for name() */
 	struct slnod	*staklist;	/* link list of function stacks */
 	int		states;		/* shell state bits used by sh_isstate(), etc. */
@@ -163,12 +163,12 @@ struct shared
 	char		*lastarg; \
 	char		*lastpath;	/* last absolute path found */ \
 	int		path_err;	/* last error on path search */ \
-	Dt_t		*track_tree;	/* for tracked aliases*/ \
+	Dt_t		*track_tree;	/* for tracked aliases */ \
 	Dt_t		*var_base;	/* global level variables */ \
 	Dt_t		*openmatch; \
-	Namval_t	*namespace;	/* current active namespace*/ \
-	Namval_t	*last_table;	/* last table used in last nv_open  */ \
-	Namval_t	*prev_table;	/* previous table used in nv_open  */ \
+	Namval_t	*namespace;	/* current active namespace */ \
+	Namval_t	*last_table;	/* last table used in last nv_open */ \
+	Namval_t	*prev_table;	/* previous table used in nv_open */ \
 	Sfio_t		*outpool;	/* output stream pool */ \
 	long		timeout;	/* read timeout */ \
 	unsigned int	curenv;		/* current subshell number */ \