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/sh/parse.c

@@ -1077,7 +1077,7 @@ static struct argnod *assign(Lex_t *lexp, register struct argnod *ap, int type)
 			struct argnod *arg = lexp->arg;
 			if(n!=0)
 				sh_syntax(lexp);
-			/* check for sys5 style function */
+			/* check for SysV style function */
 			if(sh_lex(lexp)!=LPAREN || sh_lex(lexp)!=RPAREN)
 			{
 				lexp->arg = arg;
@@ -1384,7 +1384,7 @@ static Shnode_t *simple(Lex_t *lexp,int flag, struct ionod *io)
 		associative = 1;
 	}
 	t = (struct comnod*)getnode(comnod);
-	t->comio=io; /*initial io chain*/
+	t->comio=io; /* initial io chain */
 	/* set command line number for error messages */
 	t->comline = sh_getlineno(lexp);
 	argtail = &(t->comarg);