swift234

[llvm-opt] Add wrapper script "llvm-opt" that automatically loads swift llvm dylib.

This allows one to just run llvm-opt -swift-arc-optimize, etc without needing to
know anything about hooking up the dylib.

I also changed leaks-detector to use the same type of sequence of code as
llvm-opt. It was creating a folder and copying leaks-runner into the folder
instead of just copying leaks-runner into bin.

Swift SVN r21273