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/edit/edit.c

@@ -1192,7 +1192,7 @@ void	ed_putchar(register Edit_t *ep,register int c)
 #if SHOPT_ESH || SHOPT_VSH
 /*
  * returns the line and column corresponding to offset <off> in the physical buffer
- * if <cur> is non-zero and <= <off>, then correspodning <curpos> will start the search 
+ * if <cur> is non-zero and <= <off>, then corresponding <curpos> will start the search
  */
 Edpos_t ed_curpos(Edit_t *ep,genchar *phys, int off, int cur, Edpos_t curpos)
 {