Add libclang builtin headers for LLVM release 3.3 and 3.4

Copied from the ./lib/clang/3.X/include directories of the prebuilt binary releases at llvm.org, specifically
http://llvm.org/releases/3.3/clang+llvm-3.3-amd64-Ubuntu-12.04.2.tar.gz and http://llvm.org/releases/3.4/clang+llvm-3.4-x86_64-linux-gnu-ubuntu-13.10.tar.xz.

These headers don't appear to be arch dependent, so we should be good.