Frontend:

Frontend:
 added remaining integer altivec insns (phew!)
  - vsum4ubs, vsum4sbs, vsum4shs, vsum2sws, vsumsws
  - vmsummbm, vmsumuhs, vmsumshs

 various helpers to construct IR
  - expand8x16*:      sign/zero-extend V128_8x16 lanes => 2x V128_16x8
  - breakV128to4x64*: break V128 to 4xI32's, sign/zero-extend to I64's
  - mkQNarrow64to32*: un/signed saturating narrow 64 to 32
  - mkV128from4x64*:  narrow 4xI64's to 4xI32's, combine to V128_34x4

Backend:
 Iop_Add64
   - added PPC32Instr_AddSubC32: 32-bit add/sub read/write carry
 64-bit Iex_Const
 Iop_32Sto64

git-svn-id: svn://svn.valgrind.org/vex/trunk@1447