be: Enable setting of arbitrary flags for a register class in the generator script.
be: Enable setting of arbitrary flags for a register class in the generator script.

So far only "manual_ra" could be set and everything else was ignored.

MatzeB/libfirm,libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm,MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm,libfirm/libfirm,MatzeB/libfirm,MatzeB/libfirm,libfirm/libfirm