Don't abort when ralloc.c:relinquish cannot return a heap to the system.

 src/ralloc.c (relinquish): If a heap is ready to be relinquished,
 but it still has blocs in it, don't return it to the system,
 instead of aborting.  (Bug#12402)

src/ChangeLog

+2012-10-07  Eli Zaretskii  <eliz@gnu.org>
+
+	* ralloc.c (relinquish): If a heap is ready to be relinquished,
+	but it still has blocs in it, don't return it to the system,
+	instead of aborting.  (Bug#12402)
+
 2012-10-07  Jan Djärv  <jan.h.d@swipnet.se>
 	* nsterm.m (ns_dumpglyphs_image): Only draw slice of image (Bug#12506).

src/ralloc.c

@@ -327,10 +327,11 @@ relinquish (void)
 
       if ((char *)last_heap->end - (char *)last_heap->bloc_start <= excess)
 	{
-	  /* This heap should have no blocs in it.  */
+	  /* This heap should have no blocs in it.  If it does, we
+	     cannot return it to the system.  */
 	  if (last_heap->first_bloc != NIL_BLOC
 	      || last_heap->last_bloc != NIL_BLOC)
-	    emacs_abort ();
+	    return;
 
 	  /* Return the last heap, with its header, to the system.  */
 	  excess = (char *)last_heap->end - (char *)last_heap->start;