[Mesa-dev] i965: last ARB_depth_buffer_float prep!

[Eric Anholt]

Here's the last stuff I think I need to be happy to push
GL_ARB_depth_buffer_float under the GL 3.0 override.  Mostly I needed
to remove a bunch of code in order to make handling separate
stencil/HiZ for Z32_FLOAT_X24S8 sane.  I've tested the series on gen6
with hiz enabled and disabled for float depth, and I'm working on
getting gen7 usable enough that I can test it.

What's left to do it without hiding it under the override is
converting more of swrast to doing MapRenderbuffer, in order to make
the various sw fallbacks for copypixels, drawpixels, and
framebufferblit work.