Fix various minor problems and update the documentation (#237)

These are minor fixes I've accumulated over time. The following
changes are somewhat notable:

- Added a missing entry for 'typeset -s' to the man page.
- Add strftime(3) to the 'see also' section. This and the date(1)
  addition are meant to add onto the documentation for 'printf %T'.
- Removed the man page the entry for ksh reading $PWD/.profile on
  login. That feature was removed in commit aa7713c2.
- Added date(1) to the 'see also' section of the man page.
- Note that the 'hash' command can be used instead of 'alias -t' to
  workaround one of the caveats listed in the man page.
- Use an 'out of memory' error message rather than 'out of space'
  when memory allocation fails.
- Replaced backticks with quotes in some places for consistency.
- Added missing documentation for the %P date format.
- Added missing documentation for the printf %Q and %p formats
  (backported from ksh2020: https://github.com/att/ast/pull/1032).
- The comments that show each builtin's options have been updated.

src/cmd/ksh93/sh/io.c

@@ -286,7 +286,7 @@ inetopen(const char* path, int flags, Inetintr_f onintr, void* handle)
 	for (p = addr; p; p = p->ai_next)
 	{
 		/*
-		 * some api's don't take the hint
+		 * some APIs don't take the hint
 		 */
 
 		if (!p->ai_protocol)
@@ -1533,7 +1533,7 @@ static int io_heredoc(Shell_t *shp,register struct ionod *iop, const char *name,
 	{
 		/*
 		 * the locking is only needed in case & blocks process
-		 * here-docs so this can be eliminted in some cases
+		 * here-docs so this can be eliminated in some cases
 		 */
 		struct flock	lock;
 		int	fno = sffileno(shp->heredocs);
@@ -2676,4 +2676,3 @@ int sh_chdir(const char* dir)
 		errno = err;
 	return(r);
 }
-