Add header files to CMake build solution. It use globing so it doesn't need to be manually maintained, but it won't automatically detect a new header. I think this is a good compromise for the header files, since there presence in the solution is just an help for the user. Moreover, a new header is often introduced with a new cpp source file which need a makefile change, which will regenerate the solution and detect the new header.

llvm-svn: 58566