Update LLVM

This updates LLVM and includes 2 new patches.

The first one fixes a crash triggered by the mergefunc pass, it has been submitted to upstream at http://reviews.llvm.org/D5136 and got a LGTM but has not landed yet.

The second one fixes a problem with the LLVM C-API that causes a test failure with rustc. It has been submitted to upstream at http://reviews.llvm.org/D5143