glsl: Add check for unsized arrays to glsl types

glsl: Add check for unsized arrays to glsl types

The main purpose of this patch is to increase readability of
the array code by introducing is_unsized_array() to glsl_types.
Some redundent is_array() checks are also removed, and small number
of other related clean ups.

The introduction of is_unsized_array() should also make the
ARB_arrays_of_arrays code simpler and more readable when it arrives.

V2: Also replace code that checks for unsized arrays directly with the
length variable

Signed-off-by: Timothy Arceri <t_arceri@yahoo.com.au>
v3 (Paul Berry <stereotype441@gmail.com>): clean up formatting.
Separate whitespace cleanups to their own patch.

Reviewed-by: Paul Berry <stereotype441@gmail.com>