Remove the 'intrin.h' builtin header file and its tests for now.

After discussion with several people, including Doug Gregor, we've
decided to change our approach here. If you have questions about this
header file, the commit removing it, etc., please reach out to me
off-list.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156322 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed