[libc++] Rename _NOALIAS macro to _LIBCPP_NOALIAS

Summary:
For consistency, libc++ macros always start with _LIBCPP. This should
have no functionality change.

Reviewers: EricWF, mclow.lists

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Differential Revision: https://reviews.llvm.org/D58558

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@354848 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed