Cleanup

- Remove cmake file additions to enable C++11, which are no longer necessary
because llvm compiles with this on by default
- Remove workaround for itanium-abi-triple in clang tests.  It was failing
because the default triple was not in canonical form.  I've changed it
to nyuzi-none-none in the top level cmake file, which fixes about 170 tests
that were failing before.