This change adds:

- an alternative rasterizer, which rasterizes bins in a left->right &
  top->bottom linear fashion;

- triangle -> rectangle detection;

- 1:1 blit detection;

- a special TGSI -> LLVM IR code generation that uses 8-bit SSE integers
  in AoS fashion (as opposed to 32bits floats.)

Altogether these changes yield a 2x to 3x performance improvement for 2D
workloads.  It was designed to render Windows 7 Aero and other Windows
built-in 3D applications (like Windows Media Player, Internet Explorer
11, UWP applications) with minimum CPU utilization, but it should be
generally applicable to other 2D-on-3D applications, like desktop
compositors, HTML browsers, 3D based UI toolkits, etc.

This was mostly the brainchild of Keith Whitwell back in 2010.  I wrote
TGSI -> AoS translation.  And many others added bug-fixes and
enhancements over the years: Roland Scheidegger, Brian Paul, and James
Benton.

Known issues:

- piglit spec@!opengl 1.1@quad-invariance will warn that "left and right
half should match" due to rounding error difference

- These optimized paths to kick in is that depth-buffer must not be
used, so some applications which want to benefit from these improvements
might need to be modified to ensure they use painter's algorithm instead
of depth-buffers.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Acked-by: Keith Whitwell <keithw@vmware.com>

v2: Incorporate Dave Airlie feedback: cleanup LP_DEBUG_xx; shrink 3+
empty lines.
v3: silence unused var warning, adapt to new upstream code (point setup)

Part-of: <mesa/mesa!11969>