versioner: add support for __VERSIONER_NO_GUARD.
Add an attribute that tells the preprocessor not to guard a
declaration, primarily for use with symbols that get reexported by
libc++ of the form `namespace std { using ::wctrans; }`.
Bug: http://b/28178111
Change-Id: I08c8751214797e37e8f26e7f7416a19e81c2bb4c
diff --git a/libc/include/android/versioning.h b/libc/include/android/versioning.h
index 3686261..196c28e 100644
--- a/libc/include/android/versioning.h
+++ b/libc/include/android/versioning.h
@@ -27,4 +27,6 @@
#define __INTRODUCED_IN_X86(api_level) __attribute__((annotate("introduced_in_x86=" #api_level)))
#define __INTRODUCED_IN_MIPS(api_level) __attribute__((annotate("introduced_in_mips=" #api_level)))
+#define __VERSIONER_NO_GUARD __attribute__((annotate("versioner_no_guard")))
+
#endif /* ANDROID_VERSIONING_H */