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/include/regex.h

@@ -118,7 +118,7 @@
 #define REG_EBRACE	9		/* \{...\} or {...} imbalance	*/
 #define REG_BADBR	10		/* invalid {...} digits		*/
 #define REG_ERANGE	11		/* invalid [...] range endpoint	*/
-#define REG_ESPACE	12		/* out of space			*/
+#define REG_ESPACE	12		/* out of memory		*/
 #define REG_BADRPT	13		/* unary op not preceded by re	*/
 #define REG_ENULL	14		/* empty subexpr in pattern	*/
 #define REG_ECOUNT	15		/* re component count overflow	*/