[SROA] Switch the common variable name for the 'AllocaSlices' class to 'AS'.
[SROA] Switch the common variable name for the 'AllocaSlices' class to
'AS'.

Using 'S' as this was a terrible idea. Arguably, 'AS' is not much
better, but it at least follows the idea of using initialisms and
removes active confusion about the AllocaSlices variable and a Slice
variable.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@219963 91177308-0d34-0410-b5e6-96231b3b80d8

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