i965/gen6+: Add code to perform blits on the render path ("blorp").

This patch expands the "blorp" component to be able to perform blits
as well as HiZ resolves.  The new blitting code is located in
brw_blorp_blit.cpp.  This includes the necessary fragment shader code
to look up pixels in the source buffer (which is configured as a
texture) and output them to the destination buffer (which is
configured as the render target).

Most of the time the fragment shader code is simple and
straightforward, since it merely has to apply a coordinate offset,
read from the texture, and write to the render target.  However, in
the case of blitting stencil buffers, things are more complicated,
since the GPU stores stencil data using W tiling, and W tiling is not
supported for textures or render targets.  So, we set up the stencil
buffers as Y tiled, and emit fragment shader code that adjusts the
coordinates to account for the difference between W and Y tiling.
Furthermore, since a rectangular region in W tiling does not
necessarily correspond to a rectangular region in Y tiling, we widen
the rectangle primitive to the nearest tile boundary and have the
fragment shader "kill" any pixels that don't fall inside the actual
desired destination rectangle.

All of this is a necessary prerequisite for implementing MSAA, since
we'll need to be able to blit between multisample color, depth, and
stencil buffers and their non-multisampled counterparts, and none of
the existing blitting mechanisms support multisampling.

In addition, the new blitting code should speed up operations where we
previously fell back to software rasterization, such as blitting of
stencil buffers.  The current fallback sequence is: first we try to do
a blit using the hardware blitting engine.  If that fails we try to do
a blit using the render path.  If that also fails then we do the blit
using a meta-op (which may or may not fall back to software
rasterization).

Note that blitting using the render path has some limitations at the
moment: it only supports a few formats, and it doesn't support
mirroring, clipping, or scissoring.  These limitations will be
addressed in future patch series.

v2:
- Add the code that configures the WM program to
  gen{6,7}_emit_wm_config() and gen7_emit_ps_config() rather than
  creating separate ...enable() functions.
- Call intel_prepare_render before determining which miptrees we are
  blitting from/to, because it may cause miptrees to be reallocated.
- Disable blorp blits on Gen7 for now, since they aren't working yet.
i965/gen6: Initial implementation of MSAA.

This patch enables MSAA for Gen6, by modifying intel_mipmap_tree to
understand multisampled buffers, adapting the rendering pipeline setup
to enable multisampled rendering, and adding multisample resolve
operations to brw_blorp_blit.cpp. Some preparation work is also
included for Gen7, but it is not yet enabled.

MSAA support is still fairly preliminary.  In particular, the
following are not yet supported:
- Fully general blits between MSAA and non-MSAA buffers.
- Formats other than RGBA8, DEPTH24, and STENCIL8.
- Centroid interpolation.
- Coverage parameters (glSampleCoverage, GL_SAMPLE_ALPHA_TO_COVERAGE,
  GL_SAMPLE_ALPHA_TO_ONE, GL_SAMPLE_COVERAGE, GL_SAMPLE_COVERAGE_VALUE,
  GL_SAMPLE_COVERAGE_INVERT).

Fixes piglit tests "EXT_framebuffer_multisample/accuracy" on
i965/Gen6.
Quantize num_samples.  Should fix assertions on Gen7.
intel: When AUB dumping, flush before emitting final bitmap command.

When we are generating an AUB dump, we make a final call to
aub_dump_bmp() as the context is being destroyed, to ensure that any
rendering performed before the application exits can be seen during a
simulation run.  However, we were doing this before flushing the batch
buffer; as a result simulation runs would not always see the effect of
all rendering commands.

This patch flushes the batch buffer just before making the final call
to aub_dump_bmp(), to ensure that all rendering is properly captured
in the final bitmap.
intel: Bump libdrm requirement to 2.4.34.

We'll need this for annotating AUB dumps.
i965: Completely annotate the batch bo when aub dumping.

Previously, when the environment variable INTEL_DEBUG=aub was set,
mesa would simply instruct DRM to start dumping data to an .aub file,
but we would not provide DRM with any information about the format of
the data in various buffers.  As a result, a lot of the data in the
generate .aub file would be unannotated, making further data analysis
difficult.

This patch causes the entire contents of each batch buffer to be
annotated using the data in brw->state_batch_list (which was
previously used only to annotate the output of INTEL_DEBUG=bat).  This
includes data that was allocated by brw_state_batch, such as binding
tables, surface and sampler states, depth/stencil state, and so on.

The new annotation mechanism requires DRM version 2.4.34.
Blorp: implement mirroring.
Add bin/compile to .gitignore