Add an External/llvm group.
Revert "Force the External dir to exist."

This reverts commit 86552455b9ca371647d32d152aab37fc10fdcd99.
Ignore libLLVM symlinks.
Add libLLVM-3.5.dylib to the project.
Copy the libLLVM dylib into the framework bundle.
Merge pull request #3 from robrix/link-LLVM

Link LLVM