st/mesa: fix transform feedback of unsubscripted gl_ClipDistance array

gl_ClipDistance needs special treatment in form of lowering pass
which transforms gl_ClipDistance representation from float[] to
vec4[]. There are 2 implementations - at glsl linker level (enabled
by LowerClipDistance option) and at glsl_to_tgsi level (enabled
unconditionally for gallium drivers). Second implementation is
incomplete - it does not take into account transform feedback (see
commit 642e5b413e0890b2070ba78fde42db381eaf02e5 "mesa: Fix transform
feedback of unsubscripted gl_ClipDistance array" for details).

There are 2 possible fixes:
- adding transform feedback support into glsl_to_tgsi version
- ripping gl_ClipDistance support from glsl_to_tgsi and enabling
  gl_ClipDistance lowering on glsl linker side

This patch implements 2nd option. All it does is:
- reverts most of the commit 59be691638200797583bce39a83f641d30d97492
  "st/mesa: add support for gl_ClipDistance"
- changes LowerClipDistance to true

Fixes Piglit tests "EXT_transform_feedback/builtin-varyings
gl_ClipDistance[{2,3,4,5,6,7,8}]-no-subscript" at least on nv50
and evergreen cards.
nv50: fix buffer reuse issues

1) We need to insert a barrier between consecutive transform feedback calls.
2) VBO cache needs to be flushed when TFB output is used as VBO draw input.

Fixes Piglit test EXT_transform_feedback/immediate-reuse.

Thanks to Christoph Bumiller for pointing out bugs in previous versions
of this patch.
automake: Don't warn on gmake portability issues.

Even pre-automake, we rely on gmake features for pattern
substitutions, and replacing those with reams more make code is not
interesting.  This will let us turn the old Makefiles using pattern
substitutions into automake without spewing warnings.

Reviewed-by: Dan Nicholson <dbn.lists@gmail.com>
automake: Convert src/egl/Makefile to automake.
make: Fold ASM_CFLAGS into DEFINES.

Every place that uses ASM_FLAGS already uses DEFINES.  Not including
it in DEFINES is just a way to screw up potential users, as I've done
several times while working on the build system.
make: Drop HOST_CC and HOST_CFLAGS.

Except for the deleted linux-cell target, these were just the target
cc/cflags.  The only usage was for gen_matypes, which wants the
target's structure packing, not the host, anyway.
automake: Convert gen_matypes building to automake.
automake: Directly generate configs/current instead of symlinking from it.
automake: Convert src/mesa/drivers/Makefile to automake.
automake: Convert src/mapi/glapi/gen/Makefile to automake.
automake: Convert src/mapi/glapi/gen to silent build.
automake: Convert src/gallium/Makefile to automake.
automake: Convert src/mesa/drivers/x11/Makefile to automake.

The weird versioning of the libGL where the package version was sort
of expressed as a big integer is dropped.  libtool didn't like the 0
prefix, and it didn't really make sense anyway -- if you interpret it
as an integer version number, old Mesa 071200 was bigger than current
Mesa 08100.  Instead, just bump the minor version and drop the
patchlevel.
mesa: Convert gl.pc to be generated by configure.

This saves a step of mashing variables around in our Makefile.
automake: Convert osmesa.pc to be generated by configure.
automake: Move the master Mesa makefile to Makefile.old.

This will let me incrementally move stuff to automake without
converting libmesa.a all at once.
automake: Move .pc installation to automake.
automake: Move mesa subdirs processing to automake.
mesa: Move GL header installation to automake.

This cuts some cruft related to osmesa where we were being careful to
not install headers twice.
automake: Convert Mesa built sources generation to automake.