Patch #1550800: make exec a function.

Parser/Python.asdl

@@ -36,11 +36,6 @@ module Python version "$Revision$"
 	      | Import(alias* names)
 	      | ImportFrom(identifier module, alias* names, int? level)
 
-	      -- Doesn't capture requirement that locals must be
-	      -- defined if globals is
-	      -- still supports use as a function!
-	      | Exec(expr body, expr? globals, expr? locals)
-
 	      | Global(identifier* names)
 	      | Expr(expr value)
 	      | Pass | Break | Continue