docs/specs: annotate MESA_set_3dfx_mode as obsolete

Aimed to work with Glide, which hasn't been a thing in over 10 years.
There are no drivers that implement it, so annotate it as obsolete

v2: Move the extension to OLD/

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Brian Paul <brianp@vmware.com> (v1)
Reviewed-by: Adam Jackson <ajax@redhat.com> (v1)
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
2 files changed