Added warning if the profile contains a post entry.

Added warning from all programs that read the profile if the profile
contains a post entry, which is ignored, but does not contain a
postproc entry.  In other words, if you get this warning and want
to suppress it, your options include:
1) Remove your post profile entry.
2) Make your post profile entry a comment by prepending it with the #:
   comment indicator.
3) Add a postproc entry that points to the post that you use.  That can
   be viewed with "mhparam postproc".