dri: Move API version validation into dri/common.

dri: Move API version validation into dri/common.

i965, i915, radeon, r200, swrast, and nouveau were mostly trying to do the
same logic, except where they failed to.  Notably, swrast had code that
appeared to try to enable GLES1/2 but forgot to set api_mask (thus
preventing any gles context from being created), and the non-intel drivers
didn't support MESA_GL_VERSION_OVERRIDE.

nouveau still relies on _mesa_compute_version(), because I don't know what
its limits actually are, and gallium drivers don't declare limits up front
at all.  I think I've heard talk about doing so, though.

v2: Compat max version should be 30 (noted by Ken)
    Drop r100's custom max version check, too (noted by Emil Velikov)

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