mips: Perform basic 64 bit lowering.
mips: Perform basic 64 bit lowering.

Now 'long long f(void) { return 0L; }' can be translated.

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