[Piglit] gs: Test rules related to geometry shader input sizes.

[Paul Berry]

This is a re-spin of a patch called "gs: Test rules related to
geometry shader input sizes", which I've now broken up into 8
separate patches for easier review.  I believe I've addressed all
of the comments Ian made on Aug 9.

[PATCH 1/8] gs: Verify consistency checking of geometry shader input layouts.
[PATCH 2/8] gs: Verify intra-shader checking of input layout vs. explicitly sized arrays.
[PATCH 3/8] gs: Verify inter-shader checking of input layout vs. explicitly sized arrays.
[PATCH 4/8] gs: Verify intra-shader checking of input layout vs. implicitly sized arrays.
[PATCH 5/8] gs: Verify inter-shader checking of input layout vs. implicitly sized arrays.
[PATCH 6/8] gs: Verify consistency checking of explicitly sized input arrays.
[PATCH 7/8] gs: Verify checking of sized vs. unsized geometry shader input arrays.
[PATCH 8/8] gs: Verify that an error is generated if no input layout is specified.