Re-enable the C++11 modules integration test on OS X
Re-enable the C++11 modules integration test on OS X

XCode 5.1.1 has shipped with fixed SDK headers.

This reverts commit r200256.

Fixes PR18322.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@206686 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang