mesa: Fix build when building with llvmpipe

mesa: Fix build when building with llvmpipe

Add following in mesa.inc to enable llvmpipe

PACKAGECONFIG_append_x86 = " gallium-llvm gallium r600"
PACKAGECONFIG_append_x86-64 = " gallium-llvm gallium r600"

This would enable llvmpipe for swrast, to check run this

root@qemux86:~# glxinfo | grep llvm
    Device: llvmpipe (LLVM 5.0, 128 bits) (0xffffffff)
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 5.0, 128 bits)

Backport patches to support llvm 5.0.0+
Add a patch to understand llvm version when llvm is build from git/svn

Signed-off-by: Khem Raj <raj.khem@gmail.com>