Make the standalone parser return an exit code so we can automate testing.
diff --git a/glsl_parser_extras.cpp b/glsl_parser_extras.cpp
index b774d8b..a028658 100644
--- a/glsl_parser_extras.cpp
+++ b/glsl_parser_extras.cpp
@@ -657,5 +657,5 @@
 
    delete state.symbols;
 
-   return 0;
+   return state.error != 0;
 }