Check for possible stack overrun in SP execution.

sql/sp_head.cc:
  Check for possible stack overrun, in an attempt to
  handle deep recursion more gracefully.
  (Not 100% this will always helt though, but it's better than
   nothing.)

sql/sp_head.cc

@@ -277,6 +277,12 @@ sp_head::execute(THD *thd)
   int ret= 0;
   uint ip= 0;
 
+#ifndef EMBEDDED_LIBRARY
+  if (check_stack_overrun(thd, olddbptr))
+  {
+    DBUG_RETURN(-1);
+  }
+#endif
   if (olddbptr)
   {
     uint i= 0;