mesa: fix spurious wglGetProcAddress / GL_INVALID_OPERATION error

On Windows, the Piglit primitive-restart test was failing a
glGetError()==0 assertion when it was run w/out any command line
arguments.  Piglit's all.py script only runs primitive-restart
with arguments so this case isn't normally hit during a full
piglit run.

The basic problem is Microsoft's opengl32.dll calls glFlush
from wglGetProcAddress() and Piglit uses wglGetProcAddress() to
resolve glPrimitiveRestartNV() which is called inside glBegin/End.
See comments in the code for more info.

Plus, improve the comments for _mesa_alloc_dispatch_table().

Cc: <mesa-stable@lists.freedesktop.org>
Acked-by: Sinclair Yeh <syeh@vmware.com>
i965/fs: Remove dead generate_rep_fb_write prototype.

Added in commit f9dc7aab.
Revert "i965: Emit ELSE/ENDIF JIP with type D on Gen 7."

This reverts commit 54e30dbf4db437748509d1319c3f6e4185f76c69.

Will investigate after XDC.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=84557
i965/compaction: Disable compaction on SNB temporarily.

Will investigate after XDC.
freedreno/ir3: fix lockups with lame FRAG shaders

Shaders like:

  FRAG
  PROPERTY FS_COLOR0_WRITES_ALL_CBUFS 1
  DCL IN[0], GENERIC[0], PERSPECTIVE
  DCL OUT[0], COLOR
  DCL SAMP[0]
  DCL TEMP[0], LOCAL
  IMM[0] FLT32 {    0.0000,     1.0000,     0.0000,     0.0000}
    0: TEX TEMP[0], IN[0].xyyy, SAMP[0], 2D
    1: MOV OUT[0], IMM[0].xyxx
    2: END

cause unhappyness.  They have an IN[], but once this is compiled the
useless TEX instruction goes away.  Leaving a varying that is never
fetched, which makes the hw unhappy.

In the process fix a signed vs unsigned compare.  If the vertex shader
has max_reg=-1, MAX2() vs an unsigned would not give the desired result.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
freedreno/a3xx: handle VS only outputting BCOLOR

Possibly we should map the front color to black (zeroes).  But not sure
there is a way to do that without generating a shader variant.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
freedreno: query fixes

Fixes a few issues, including a potential empty-IB (which triggers gpu
hangs in piglit occlusion_query_meta_no_fragments)

Signed-off-by: Rob Clark <robclark@freedesktop.org>