[libcxx] Direct support for Fuchsia

Fuchsia's libc was forked from musl, but has evolved sufficiently
since then so it no longer makes sense to pretend it's musl. This
change implements direct support for Fuchsia rather than
piggybacking on musl support.

Differential Revision: https://reviews.llvm.org/D31970

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@300261 91177308-0d34-0410-b5e6-96231b3b80d8

include/support/fuchsia/xlocale.h

@@ -0,0 +1,23 @@
+// -*- C++ -*-
+//===------------------- support/fuchsia/xlocale.h ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_FUCHSIA_XLOCALE_H
+#define _LIBCPP_SUPPORT_FUCHSIA_XLOCALE_H
+
+#if defined(__Fuchsia__)
+
+#include <cstdlib>
+#include <cwchar>
+#include <support/xlocale/__posix_l_fallback.h>
+#include <support/xlocale/__strtonum_fallback.h>
+
+#endif // defined(__Fuchsia__)
+
+#endif // _LIBCPP_SUPPORT_FUCHSIA_XLOCALE_H