mesa: accept TYPE_PUSH/POP_GROUP with glDebugMessageInsert

mesa: accept TYPE_PUSH/POP_GROUP with glDebugMessageInsert

These new (relative to ARB_debug_output) tokens, have been explicitly
separated from the existing ones in the spec text. With the reference
to glDebugMessageInsert was dropped.

At the same time, further down the spec says:
   "The value of <type> must be one of the values from Table 5.4"

... and these two are listed in Table 5.4.

The GL 4.3 and GLES 3.2 do not give any hints on the former
'definition', plus CTS requires that the tokens are valid values for
glDebugMessageInsert.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>