Check-in together with libGLw!

- removed no longer needed ncurses-devel BuildRequires (boo#1082315)

- redone u_add_llvm_codegen_dependencies.patch and renamed to
u_configure.ac-Link-to-libLLVMCodegen-to-fix-cyclic-li.patch
(boo#1082307)

- removed u_mesa-8.0.1-fix-16bpp.patch and
u_mesa-8.0-llvmpipe-shmget.patch, which we no longer apply since
about 5 years (boo#1082305)

- recreated u_mesa-python3-only.patch and renamed to
u_r600-egd_tables.py-added-support-for-python-3.patch; also
removed first hunk (boo#1082303)

- removed n_Define-GLAPIVAR-separate-from-GLAPI.patch
* bits moved to libGLw's n_Use-newly-introduced-GLAPIVAR-for-variables.patch
(boo#1082297)

- Mesa-gallium only exists if %{with_opencl}
- Add support for riscv64