Fix major bug in thunk detection. Also verify the calling convention.
Fix major bug in thunk detection. Also verify the calling convention.

Switch from isWeakForLinker to mayBeOverridden which is more accurate.

Add more statistics and debugging info. Add comments. Move static function
outside anonymous namespace.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@113190 91177308-0d34-0410-b5e6-96231b3b80d8

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