main/fbobject: implement new 4.5 pnames for GetFramebufferParameter

main/fbobject: implement new 4.5 pnames for GetFramebufferParameter

4.5 added new pnames allowed for GetFramebufferParameter, and
GetNamedFramebufferParameter.

From OpenGL 4.5 spec, section 9.2.3 "Framebuffer Object Queries" (quoting
the paragraph with only the new pnames, not all the supported):

   "pname may also be one of DOUBLEBUFFER,
    IMPLEMENTATION_COLOR_READ_FORMAT, IMPLEMENTATION_COLOR_READ_TYPE,
    SAMPLES, SAMPLE_BUFFERS, or STEREO, indicating the corresponding
    framebuffer-dependent state from table 23.73. Values of
    framebuffer-dependent state are identical to those that would be
    obtained were the framebuffer object bound and queried using the
    simple state queries in that table. These values may be queried
    from either a framebuffer object or a default framebuffer."

Fixes:
GL45-CTS.direct_state_access.framebuffers_get_parameters

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>