Use the same definition for ClassBase#== on all platforms
Use the same definition for ClassBase#== on all platforms

This means the implementation is slightly slower than necessary on
non-java platforms, but this seems a reasonable tradeoff for removing
complexity.

jcupitt/gir_ffi,mvz/gir_ffi,mvz/gir_ffi,jcupitt/gir_ffi,mvz/gir_ffi