added ambient parameter in global options{} for parser to set scene's global ambient color

git-svn-id: svn://anubis/fart/trunk@260 7f9b0f55-74a9-4bce-be96-3c2cd072584d

parser/parser.yy

@@ -311,6 +311,9 @@ options_item: WIDTH DEC_NUMBER {
             | EXPOSURE number {
                     $$ = new ExposureNode($2->getNumber());
                 }
+            | AMBIENT vector {
+                    $$ = new AmbientNode($2->getVector());
+                }
             ;
 
 plane: PLANE LCURLY plane_items RCURLY {