COMP: Split conversion of asm sources to C literals in header files out into vtkVRASM.cmake.  The cmake code is now included for most generators, but for CMake 2.0's Makefile generator it is included in a special VTKVRASM project during a try-compile.  This ensures the generated headers exist after CMake runs so that a parallel make will not cause multiple local generates at the same time.  Such a hack is not needed for CMake 2.2 and above.