Add support for Ananas platform

Ananas is a home-brew operating system, mainly for amd64 machines. After
using GCC for quite some time, it has switched to clang and never looked
back - yet, having to manually patch things is annoying, so it'd be much
nicer if this was in the official tree.

More information:

https://github.com/zhmu/ananas/
https://rink.nu/projects/ananas.html

Submitted by:	Rink Springer
Differential Revision:	https://reviews.llvm.org/D32936


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@306239 91177308-0d34-0410-b5e6-96231b3b80d8