mesa: enable GL_TEXTURE_LOD_BIAS set/get

mesa: enable GL_TEXTURE_LOD_BIAS set/get

Earlier comments suggest this was removed from GL core spec but it is
still there. Enabling makes 'texture_lod_bias_getter' Khronos
conformance tests pass, also removes some errors from Metro Last Light
game which is using this API.

v2: leave NOTE comment (Ian)

Cc: "9.0 9.1 9.2 10.0" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>