Bison 3 fixes.

--- src/mtgrammar.y.orig	Sat Nov  7 16:02:08 2015
+++ src/mtgrammar.y	Sat Nov  7 16:02:55 2015
@@ -57,7 +57,7 @@ static void yyprint (/*FILE *p_file, int p_type, YYSTY
 
 %}
 
-%pure_parser 
+%define api.pure
 
 %union {
   mttok tok;