After some discussion with Doug, we decided that it made a lot more sense

After some discussion with Doug, we decided that it made a lot more sense
for __unknown_anytype resolution to destructively modify the AST.  So that's
what it does now, which significantly simplifies some of the implementation.
Normal member calls work pretty cleanly now, and I added support for
propagating unknown-ness through &.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129331 91177308-0d34-0410-b5e6-96231b3b80d8