Remove XFAIL from a number of tests that aren't expected to fail

These tests haven't been failing on darwin11 or 12 since r189610 when
pr17027 was fixed, but they've been keeping the libc++ bot red by
XPASSing since then.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@208831 91177308-0d34-0410-b5e6-96231b3b80d8