implement lvalue to rvalue conversion for ocuvector components. We can now compile stuff

like this:

typedef __attribute__(( ocu_vector_type(4) )) float float4;
float4 test1(float4 V) {
  return V.wzyx+V;
}

to:
_test1:
        pshufd  $27, %xmm0, %xmm1
        addps   %xmm0, %xmm1
        movaps  %xmm1, %xmm0
        ret

and:

_test1:
        mfspr r2, 256
        oris r3, r2, 4096
        mtspr 256, r3
        li r3, lo16(LCPI1_0)
        lis r4, ha16(LCPI1_0)
        lvx v3, r4, r3
        vperm v3, v2, v2, v3
        vaddfp v2, v3, v2
        mtspr 256, r2
        blr 

llvm-svn: 40771