Implement framework for scalarizing node results. This is sufficient

Implement framework for scalarizing node results.  This is sufficient
to codegen this:

define float @test_extract_elt(<1 x float> * %P) {
	%p = load <1 x float>* %P
	%R = extractelement <1 x float> %p, i32 0
	ret float %R
}

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44570 91177308-0d34-0410-b5e6-96231b3b80d8