arb-fragment-coord-conventions: test center shift correctness

Modifies the pixel center tests to check that the pixel coordinates
actually start at 0 / 0.5.
Catches sign errors in center shift calculation (+-0.5).
gl-1.0-dlist-shademodel: test glShadeModel() inside a display list

This is pretty trivial, but it's useful for debugging a Mesa display
list optimization.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
dlist-beginend: test some tricky glBegin/glEnd display list corner cases

These are some special cases not covered by the beginend-coverage test.
In particular, we do some drawing/probing.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
gl-1.0-begend-coverage: remove unneeded #include "minmax-test.h"

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
gl-1.0-beginend-coverage: fix FBO-related failures when using GLUT

When Piglit's configured to use GLUT instead of Waffle we don't have
full support for the -fbo option.  So in beginend-coverage we now
check if we really have a FBO bound in order to compute the right
fbo_attachment value.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
s3tc-errors: add more glTex[Sub]Image2D() error checking tests

Two new things:
1. Test small mipmap level sizes (width,height=1,2,4)
2. Test NPOT textures

Passes with NVIDIA's driver.  Checks for a Mesa bug.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Eric Anholt <eric@anholt.net>