main/get: make KHR_debug enums available everywhere

main/get: make KHR_debug enums available everywhere

Move all the enums but CONTEXT_FLAGS. The spec seems quite explicit
about the latter (wrt OpenGL ES)

    "In OpenGL ES versions prior to and including ES 3.1 there is no
    CONTEXT_FLAGS state and therefore the CONTEXT_FLAG_DEBUG_BIT cannot
    be queried."

v2 [Emil Velikov] Rebase.
v3 [Emil Veliokv] Drop the CONTEXT_FLAGS hunk - not applicable for GLES

Signed-off-by: Matthew Waters <ystreet00@gmail.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>