Revert r248483, r242546, r242545, and r242409 - absdiff intrinsics

Revert r248483, r242546, r242545, and r242409 - absdiff intrinsics

After much discussion, ending here:

  http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151123/315620.html

it has been decided that, instead of having the vectorizer directly generate
special absdiff and horizontal-add intrinsics, we'll recognize the relevant
reduction patterns during CodeGen. Accordingly, these intrinsics are not needed
(the operations they represent can be pattern matched, as is already done in
some backends). Thus, we're backing these out in favor of the current
development work.

r248483 - Codegen: Fix llvm.*absdiff semantic.
r242546 - [ARM] Use [SU]ABSDIFF nodes instead of intrinsics for VABD/VABA
r242545 - [AArch64] Use [SU]ABSDIFF nodes instead of intrinsics for ABD/ABA
r242409 - [Codegen] Add intrinsics 'absdiff' and corresponding SDNodes for absolute difference operation

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255387 91177308-0d34-0410-b5e6-96231b3b80d8