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/name.c

@@ -82,7 +82,7 @@ struct adata
 	short		numnodes;
 	short		maxnodes;
     };
-#endif /*SHOPT_TYPEDEF */
+#endif /* SHOPT_TYPEDEF */
 
 #if NVCACHE
     struct Namcache
@@ -1227,7 +1227,7 @@ Namval_t *nv_create(const char *name,  Dt_t *root, int flags, Namfun_t *dp)
  * delete the node <np> from the dictionary <root> and clear from the cache
  * if <root> is NULL, only the cache is cleared
  * if flags does not contain NV_NOFREE, the node is freed
- * if np==0  && !root && flags==0,  delete the Refdict dictionary
+ * if np==0 && !root && flags==0, delete the Refdict dictionary
  */
 void nv_delete(Namval_t* np, Dt_t *root, int flags)
 {
@@ -2232,7 +2232,7 @@ static int scanfilter(Dt_t *dict, void *arg, void *data)
 #if SHOPT_TYPEDEF
 	if(!is_abuiltin(np) && tp && tp->tp && nv_type(np)!=tp->tp)
 		return(0);
-#endif /*SHOPT_TYPEDEF */
+#endif /* SHOPT_TYPEDEF */
 	if(sp->scanmask==NV_TABLE && nv_isvtree(np))
 		k = NV_TABLE;
 	if(sp->scanmask?(k&sp->scanmask)==sp->scanflags:(!sp->scanflags || (k&sp->scanflags)))