Check type attribute for ull == GLuint64. Fixes #24

In line 2351 of gl.xml there's an attribute called type. This is set to "ull" (I believe short for unsigned long long) for GL_TIMEOUT_IGNORED. As seen [in the OpenGL docs](http://www.opengl.org/sdk/docs/man4/xhtml/glWaitSync.xml) this should be matched to `GLuint64`.