Change DiffFilesWithTolerance to be written in terms of MemoryBuffer, not an mmapped file.  This more closely matches its requirements and provides an implicitly null terminated buffer, something this routine had to emulate itself before.
Change DiffFilesWithTolerance to be written in terms of MemoryBuffer,
not an mmapped file.  This more closely matches its requirements and
provides an implicitly null terminated buffer, something this
routine had to emulate itself before.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@49024 91177308-0d34-0410-b5e6-96231b3b80d8

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