mesa: fix maximum allowed proxy texture size condition

mesa: fix maximum allowed proxy texture size condition

width, height parameter in glTexImage2D() includes: texture image
width + 2 * border (if any). So when doing the texture size check
in _mesa_test_proxy_teximage() width and height should not exceed
maximum supported size for target texture type + 2 * border.
i.e. 1 << (ctx->Const.MaxTextureLevels - 1) + 2 * border

Texture border is anyway stripped out before it is given to intel
or gallium drivers.

This patch fixes Intel oglconform test case:
max_values negative.textureSize.textureCube
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44970

Note: This is a candidate for mesa 8.0 branch.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Ian Romanick <idr@freedesktop.org>
Reviewed-by: Brian Paul <brianp@vmware.com>