tcg-ppc64: Merge ppc32 shifts

Signed-off-by: Richard Henderson <rth@twiddle.net>
target-alpha: Don't issue goto_tb under singlestep

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-ppc64: Fix sub2 implementation

All sorts of confusion on argument ordering.

Signed-off-by: Richard Henderson <rth@twiddle.net>
fixup! tcg-ppc64: Support muluh_i32 and mulsh_i32