[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

llvm-svn: 354848
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 5d79eaa82f6f6f729784bb422576f96ae445118d
diff --git a/include/__config b/include/__config
index 3ca6615..5ca60d6 100644
--- a/include/__config
+++ b/include/__config
@@ -910,9 +910,9 @@
 #endif
 
 #ifdef __GNUC__
-#  define _NOALIAS __attribute__((__malloc__))
+#  define _LIBCPP_NOALIAS __attribute__((__malloc__))
 #else
-#  define _NOALIAS
+#  define _LIBCPP_NOALIAS
 #endif
 
 #if __has_feature(cxx_explicit_conversions) || defined(__IBMCPP__) || \