mesa: Refactor error checking for GL_TEXTURE_BASE_LEVEL vs texture targets
Add a big spec quotation justifying the error generated, which has changed over the GL versions. v2: Compact the spec quote based on a Khronos bug and discussion with Jason. Signed-off-by:Ian Romanick <ian.d.romanick@intel.com> Reviewed-by:
Jason Ekstrand <jason.ekstrand@intel.com>