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/sfsetbuf.c

@@ -410,7 +410,7 @@ done:
 	_Sfi = f->val = obuf ? osize : 0;
 
 	/* blksz is used for aligning disk block boundary while reading data to
-	** optimize data transfer from disk (eg, via direct I/O). blksz can be
+	** optimize data transfer from disk (e.g., via direct I/O). blksz can be
 	** at most f->size/2 so that data movement in buffer can be optimized.
 	** blksz should also be a power-of-2 for optimal disk seeks.
 	*/