gallivm: more integer texture format fetch fixes

Change the texel type to int/uint instead of float throughout the sampling
code which makes it easier to catch errors (as llvm will complain about wrong
types if we mistakenly treat these values as real floats somewhere).
This should also get things like e.g. sampler swizzles (for unused channels)
right.
This fixes piglit texture_integer_glsl130 test.
Border color not working (crashing) yet.
(These formats are not exposed yet in llvmpipe.)

v2: couple cleanups according to José's comments

Reviewed-by: José Fonseca <jfonseca@vmware.com>
gallivm: fix border color for integer textures

Need to bitcast the float border color (luckily we already get
the color as int just disguised as float).
Fixes piglit texwrap GL_EXT_texture_integer bordercolor.

Reviewed-by: José Fonseca <jfonseca@vmware.com>
llvmpipe: fix clearing integer color buffers

We get int/uint clear color value in this case, and util_pack_color can't
handle these formats at all (even if it could, float input color isn't what
we want).
Pass through the color union appropriately and handle the packing ourselves
(as I couldn't think of a good generic util solution).
This gets piglit fbo_integer_precision_clear and
fbo_integer_readpixels_sint_uint from the ext_texture_integer test group from
segfault to pass (which only leaves fbo-blending from that group not working).

v2: fix up comments
targets/dri-swrast: Force c++ linker in all cases.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=59226

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Andreas Boll <andreas.boll.dev@gmail.com>
Tested-by: Vinson Lee <vlee@freedesktop.org>
targets/egl-static: fix link failure to libwayland-drm

Fixes the following build error:
  CXXLD    egl_gallium.la
g++: error: ../../../../src/egl/wayland/wayland-drm/.libs/.libs/libwayland-drm.a: No
such file or directory

Reviewed-by: Andreas Boll <andreas.boll.dev@gmail.com>
glcpp: Add back tests/*.out to .gitignore

Accidentally removed in ac2793cf3e1e004942c386dfa45f3b5507223f50
Remove hacks for static Makefiles

v2: Andreas Boll <andreas.boll.dev@gmail.com>
    - don't remove compatibility with scripts for the old build system

v3: Andreas Boll <andreas.boll.dev@gmail.com>
    - remove more obsolete hacks

v4: Andreas Boll <andreas.boll.dev@gmail.com>
    - add a previously removed TOP variable to fix vgapi build
glapi/gen: remove an obsolete comment from Makefile.am
mesa/dricore: Drop compatibility for the old Mesa build system and -avoid-version.
Drop last parts of compatibility for the old Mesa build system.
gallium/auxiliary: Build libgallium 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.
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.
Clang should warn only about unused CFLAGS and CXXFLAGS on debug builds.
tests: AM_CPPFLAGS must include $(top_srcdir) instead of $(top_builddir).
gtest: Build it only for 'make check'.
radeon, clover: Make it compile on LLVM >= r171366.