Fix compilation error when MALLOC_DEBUG is enabled

To fix a memory leak in CEL, a channel datastore was introduced whose
destruction function pointer was pointed to the ast_free macro.  Without
MALLOC_DEBUG enabled this compiles as fine, as ast_free is defined as free.
With MALLOC_DEBUG enabled, however, ast_free takes on a definition from a
different place then utils.h, and became undefined.  This patch resolves this
by using a reference to ast_free_ptr.  When MALLOC_DEBUG is enabled, this
calls ast_free; when MALLOC_DEBUG is not enabled, this is defined to be
ast_free, which is defined to be free.

(issue AST-916)
Reported by: Thomas Arimont
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Merged revisions 370273 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 370274 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@370276 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/cel.c

@@ -395,7 +395,7 @@ void ast_cel_check_retire_linkedid(struct ast_channel *chan)
  */
 static const struct ast_datastore_info fabricated_channel_datastore = {
 	.type = "CEL fabricated channel",
-	.destroy = ast_free,
+	.destroy = ast_free_ptr,
 };
 
 struct ast_channel *ast_cel_fabricate_channel_from_event(const struct ast_event *event)