Add some more immediate patterns. This allows us to compile:

void test6() {
  Y = 0xABCD0123BCDE4567;
}

into:

_test6:
        lis r2, -21555
        lis r3, ha16(_Y)
        ori r2, r2, 291
        rldicr r2, r2, 32, 31
        oris r2, r2, 48350
        ori r2, r2, 17767
        std r2, lo16(_Y)(r3)
        blr

llvm-svn: 28885