xlib: handle _mesa_initialize_visual()'s return value

If the call fails, we should return NULL from XMesaCreateVisual().
This was found when Waffle tried to create a visual with depth/stencil
bits = -1.  That's an illegal value for glXChooseFBConfig() and we should
return NULL in that situation.

Note: This is a candidate for the stable branches.
glsl: add cast to silence signed/unsigned comparision warning
mesa: fix signed/unsignd mix-up in fetch_signed_l_latc1()

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=58844
mesa: Fix error reporting in _mesa_invalidate_pbo_{compressed_,}teximage.

The old error reporting was completely bogus, passing _mesa_error() a
format string that didn't even match the remaining arguments.  Also,
in many cases the number of dimensions in the TexImage call was not
preserved in the error message (e.g. an error in glTexImage2D was
reported simply as an error in glTexImage).

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
mesa: Implement compressed 2D array textures.

This patch adds functionality to Mesa to upload compressed
2-dimensional array textures, using the glCompressedTexImage3D and
glCompressedTexSubImage3D calls.

Fixes piglit tests "EXT_texture_array/compressed *" and "!OpenGL ES
3.0/ext_texture_array-compressed_gles3 *".  Also partially fixes GLES3
conformance test "CoverageES30.test".

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
i965: Fix glCompressedTexSubImage2D offsets for ETC textures.

This patch fixes intel_miptree_unmap_etc() (which decompresses ETC
textures to linear) to pay attention to map->x and map->y when writing
to the destination image.  Previously these values were ignored,
causing the xoffset and yoffset parameters passed to
glCompressedTexSubImage2D() to be ignored.
mesa: Add ALIGN() macro to main/macros.h.

Previously this macro existed in 3 separate places, some inside the
intel driver and some outside of it.  It makes more sense to have it
in main/macros.h
glsl: Separate varying linking code to its own file.

linker.cpp is getting pretty big, and we're about to add even more
varying packing code, so split out the linker code that concerns
varyings to its own file.
glsl: Plumb through is_parameter to apply_type_qualifier_to_variable()

This patch adds logic to allow the ast_to_hir function
apply_type_qualifier_to_variable() to tell whether it is acting on a
variable declaration or a function parameter.  This will allow it to
correctly interpret the meaning of "out" and "in" keywords (which have
different meanings in those two contexts).
glsl: Prohibit structs and bools from being used as "varyings".

The GLSL 1.30 spec only allows vertex shader outputs and fragment
shader inputs ("varyings" in pre-GLSL-1.30 parlance) to be of type
int, uint, float, or vectors, matrices, or arrays thereof.  Bools,
bvec's, and structs are prohibited.  (Integral varyings were
prohibited prior to GLSL 1.30).

Previously, Mesa only performed this check on variables declared with
the "varying" keyword, and it always performed the check according to
the pre-GLSL-1.30 rules.  As a result, bools and structs were allowed
to slip through, provided they were declared using the new in/out
syntax.

This patch modifies the error check so that it occurs after "varying"
is converted to "in/out", and corrects it to properly account for GLSL
version.

Fixes piglit tests:
  in-bool-prohibited.frag
  in-bvec2-prohibited.frag
  in-bvec3-prohibited.frag
  in-bvec4-prohibited.frag
  in-struct-prohibited.frag
  out-bool-prohibited.vert
  out-bvec2-prohibited.vert
  out-bvec3-prohibited.vert
  out-bvec4-prohibited.vert
  out-struct-prohibited.vert
glsl: Pack flat "varyings" of mixed types together.

This patch enhances the varying packing code so that flat varyings of
uint, int, and float types can be packed together.

We accomplish this in lower_packed_varyings.cpp by making the type of
all flat varyings ivec4, and then using information-preserving type
conversions (e.g. ir_unop_bitcast_f2i) to convert all other types to
ints.

The varying_matches::compute_packing_class() function is updated to
reflect the fact that varying packing no longer needs to segregate
varyings of different base types.

Fixes piglit test varying-packing-mixed-types.