Fix OpenGL object label queries.
Fix OpenGL object label queries.

Passing 0 as bufSize to glGetObjectLabel() is not allowed by the spec
even when just querying the size, thus passing the maximum. Might
hopefully fix the label queries on AMD drivers.

DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,MiUishadow/magnum