r300g: kill the X.Org state tracker target

This won't ever be made default and we don't need it anyway.

We should also consider doing this for other drivers.
r300g: random hyperz cleanups
r300g: allow HiZ with a 16-bit zbuffer
r300g: if both Z and stencil are present, they must be fast-cleared together
r300g: allow separate depth and stencil clear

The handling of the CAP is broken in st/mesa anyway. Let's just kill it.

This commit pretty much enables fast Z clear for FBOs with Z24S8.
The driver falls back to clearing with a quad if the fast clear cannot be
used. It can still do fast color clear, for example.
r300g: advertise MSAA support for the RGB10_A2 format on r500

It seems to be working just fine.
r300g: fix MSAA resolve to an untiled texture

RB3D_DEBUG_CTL doesn't help, so I resolve to a tiled temporary texture and
then blitting it to the destination one, which we also do in other situations.
radeon, clover: Make it compile on LLVM >= r171366.
gallium/svga: Make sure -std=gnu99 is set.
configure.ac: Save user {C,CXX}FLAGS and append them at end.

This way the user has the privilege of last decision and so the option to build an optimized debug build again.
Suppress clang's warnings about unused CFLAGS and CXXFLAGS.
gallium/auxiliary: Build libgallium shared.
Drop last parts of compatibility for the old Mesa build system.
mapi: Build libglapi always shared.
mesa: Build libmesa shared.
Install all internal shared libs to $(libdir)/mesa-$VERSION.
Makefile.am: s:-no-undefined:-Wl,--no-undefined to make it work.
gallium/drivers: Build libs -shared.
i915: Conditionally build an i915g driver instead of two i915 drivers.