mesa: Make Mesa core set up wrapped texture renderbuffer state.

mesa: Make Mesa core set up wrapped texture renderbuffer state.

Everyone was doing effectively the same thing, except for some funky code
reuse in Intel, and swrast mistakenly recomputing _BaseFormat instead of
using the texture's _BaseFormat.  swrast's sRGB handling is left in place,
though it should be done by using _mesa_get_render_format() at render time
instead (as-is, it will miss updates to GL_FRAMEBUFFER_SRGB).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>