CMake: separate out a few C++ files from lib/CL into CMake "object" library.
CMake: separate out a few C++ files from lib/CL into CMake "object" library.

This has essentially no effect except that it adds a new
build system target "lib_cl_llvm". This makes it easier
to build those files on machines with low RAM, while building
the rest of pocl in parallel.

Oblomov/pocl,pocl/pocl,franz/pocl,franz/pocl,pocl/pocl,pocl/pocl,Oblomov/pocl,franz/pocl,pocl/pocl,Oblomov/pocl,franz/pocl,pocl/pocl,Oblomov/pocl,franz/pocl,Oblomov/pocl