[COMMIT] Fix some bugs in #'substitute, #'nsubstitute.

Aidan Kehoe writes:

 > +;; Test #'substitute. Paul Dietz has much more comprehensive
 > tests.

What was the issue with adding the Dietz suite to XEmacs?  License?

 > APPROVE COMMIT
 > 
 > NOTE: This patch has been committed.

Thanks much!  Especially for the tests!

 > # HG changeset patch
 > # User Aidan Kehoe <[email protected]>
 > # Date 1425484440 0
 > #      Wed Mar 04 15:54:00 2015 +0000
 > # Node ID e9bb3688e654d8f944fbf2943f9f9d030e272501
 > # Parent  eabf763bc6f95812d41b72436de9cd1ab73f7737
 > Fix some bugs in #'substitute, #'nsubstitute.
 > 
 > src/ChangeLog addition:
 > 
 > 2015-03-04  Aidan Kehoe  <[email protected]>
 > 
 > 	* sequence.c (count_with_tail):
 > 	Accept COUNT from #'substitute, #'nsubstitute too.
 > 	* sequence.c (FdeleteX):
 > 	Only remove COUNT from the arguments if FROM-END is non-nil.
 > 	* sequence.c (Fnsubstitute):
 > 	Remove COUNT from the arguments if specified and FROM-END is
 > 	non-nil.
 > 	* sequence.c (Fsubstitute):
 > 	Remove COUNT from the arguments if specified and FROM-END is
 > 	non-nil. Do this before calling count_with_tail(). When we
 > 	encounter the cons return by count_with_tail(), use the
 > 	replacement object.
 > 
 > 
 > tests/ChangeLog addition:
 > 
 > 2015-03-04  Aidan Kehoe  <[email protected]>
 > 
 > 	* automated/lisp-tests.el:
 > 	Add some tests for #'substitute.