glsl: Restrict functions to not return arrays or SOAs in GLSL 1.00.

glsl: Restrict functions to not return arrays or SOAs in GLSL 1.00.

From the spec,

    Arrays are allowed as arguments, but not as the return type. [...] The
    return type can also be a structure if the structure does not contain
    an array.

Fixes DEQP shaders.functions.invalid.return_array_in_struct_fragment.

v2: Spec cite wording change

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Matt Turner <mattst88@gmail.com>