glsl: allow bindless samplers/images inside interface blocks

glsl: allow bindless samplers/images inside interface blocks

From section 4.3.7 of the ARB_bindless_texture spec:

   "(remove the following bullet from the last list on p. 39, thereby
    permitting sampler types in interface blocks; image types are also
    permitted in blocks by this extension)"

    * sampler types are not allowed

v3: - update the spec comment
    - update the glsl error message

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>