This patch intends to support program link validation on geometry
shader itself. A link error should occur when linking a program with
a geometry shader that lacks input primitive or output primitive or
the declaration of 'max_vertices'.

This patch also adds the support of linking a program with geometry
shader in angle_end2end_tests.

BUG=angleproject:1941
TEST=angle_end2end_tests
     dEQP-GLES31.functional.shaders.linkage.es31.geometry.varying.rules.unspecified_*

Change-Id: I25fb08514753102f5dd3ab86211c05d2ca4fd185
Reviewed-on: https://chromium-review.googlesource.com/898842
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>