Revert "Add builtin includes for AppleClang 5.1"

This reverts commit c62bb98f4f4ca52fcb765bb81b526ceb433ae157.
Revert "Add libclang builtin headers for LLVM release 3.3 and 3.4"

This reverts commit 2f84503a99bc1be474719d42ffdc42e5d0de215b.
Revert "Don't pass extra include path to libclang"

This reverts commit 7bdff8941c1bcb8df3badbef403927211cb3391a.
Revert "Remove clang_includes folder"

This reverts commit cca4785fb69740f36b6d07280d2fb4d6dc039e62.