mesa: Only require Gen'ed name for glBind{Framebuffer,Renderbuffer} on desktop

mesa: Only require Gen'ed name for glBind{Framebuffer,Renderbuffer} on desktop

Desktop OpenGL implementations that support either
GL_ARB_framebuffer_object or OpenGL 3.0 must require names from
glGenFramebuffers for glBindFramebuffer.  We have enforced this rule for
quite some time.  However, OpenGL ES 1.0, 2.0, and 3.0 implementations
are required to allow user-defined names (e.g., not from
glGenFramebuffers{OES,}).

The Intel drivers have hacked around this by not enabling
GL_ARB_framebuffer_object in an ES context.  Instead, just pick the
correct behavior in _mesa_BindFramebuffer based on the context API.

Chad pointed out in a review e-mail:

    "I'd like to point out, though, that glBindFramebufferEXT and
    glBindRenderbufferEXT are still broken on desktop GL because they
    don't accept user-genned names. But that fix belongs to a different
    series."

Currently glBindFramebufferEXT is an alias for glBindFramebuffer.
Unalising two functions presents some difficulty, so we'll have to
revisit this eventually.

v2: Perform same check in _mesa_BindRenderbuffer too.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> [v1]