Revert "Update to LLVM 3.2" to work around issues on OS X. If the LLVM 3.2
headers are compiled under -std=c++11 they expect to find a definition of
std::move in <utility>, but this requires also requires the -stdlib=libc++
option.

This reverts commit 79e2b2d919ef21cc393a7d29bc3a7c4209ba0ef0.
Disable X in SDL build on OS X.