[SCEV] Extract out a MatchBinaryOp; NFCI
[SCEV] Extract out a MatchBinaryOp; NFCI

MatchBinaryOp abstracts out the IR instructions from the operations they
represent.  While this change is NFC, we will use this factoring later
to map things like `(extractvalue 0 (sadd.with.overflow X Y))` to `(add
X Y)`.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@264747 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm