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/sfio/sftmp.c

@@ -218,7 +218,7 @@ Sfio_t*	f;
 # if defined(__linux__) && _lib_statfs
 	/*
 	 * Use the area of POSIX shared memory objects for the new temporary file descriptor
-	 * that is do not access HD or SSD but only the memory based tmpfs of the POSIX SHM
+	 * that is do not access the HDD or SSD but only the memory based tmpfs of the POSIX SHM
 	 */
 	static int doshm;
 	static char *shm = "/dev/shm";