Upgrade LLVM with iOS/OS X fixes

SjLj fix landed three weeks ago, but OS X build was broken when targeting 10.5 (which is by default for Rust) and fix for that landed 1 hour ago.

It might require small changes in LLVM wrapper in main repo, will do them tomorrow.

Number of commits looks extremely huge, but it should be OK, considering that a month passed since last full LLVM update.