glsl-1.50: Test illegal uses of unsized arrays in interface blocks.

These tests verify that unsized arrays appearing inside interface
blocks are subject to the same restrictions as unsized arrays
appearing outside interface blocks (e.g. they can't be used in bulk
assignment, they don't support .length(), and they can't be accessed
using a non-constant index).

Since it's likely that these restrictions are enforced by the same
code as for unsized arrays appearing outside of interface blocks,
these are just a few touch tests; we don't exhaustively test all
possible types of access in every shader type.