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/lib/libast/port/astconf.c

@@ -813,7 +813,7 @@ feature(register Feature_t* fp, const char* name, const char* path, const char*
 		if (!(fp = newof(0, Feature_t, 1, n + 1)))
 		{
 			if (conferror)
-				(*conferror)(&state, &state, 2, "%s: out of space", name);
+				(*conferror)(&state, &state, 2, "%s: out of memory", name);
 			return 0;
 		}
 		fp->op = -1;