[SROA] Start more deeply moving SROA to use ranges rather than just iterators.
[SROA] Start more deeply moving SROA to use ranges rather than just
iterators.

There are a ton of places where it essentially wants ranges
rather than just iterators. This is just the first step that adds the
core slice range typedefs and uses them in a couple of places. I still
have to explicitly construct them because they've not been punched
throughout the entire set of code. More range-based cleanups incoming.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@219955 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,dslab-epfl/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,dslab-epfl/asap,dslab-epfl/asap,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,dslab-epfl/asap,llvm-mirror/llvm,apple/swift-llvm