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.
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.