_FORTIFY_SOURCE: add memset / bzero support

Add _FORTIFY_SOURCE support for the following functions:

* memset
* bzero

Move the __BIONIC_FORTIFY_INLINE definition to cdefs.h so it
can be used from multiple header files.

Change-Id: Iead4d5e35de6ec97786d58ee12573f9b11135bb7
diff --git a/libc/include/strings.h b/libc/include/strings.h
index fee7dc4..db2aa3a 100644
--- a/libc/include/strings.h
+++ b/libc/include/strings.h
@@ -51,6 +51,14 @@
 char	*rindex(const char *, int);
 int	 strcasecmp(const char *, const char *);
 int	 strncasecmp(const char *, const char *, size_t);
+
+#if defined(__BIONIC_FORTIFY_INLINE)
+__BIONIC_FORTIFY_INLINE
+void bzero (void *s, size_t n) {
+    __builtin___memset_chk(s, '\0', n, __builtin_object_size (s, 0));
+}
+#endif /* defined(__BIONIC_FORTIFY_INLINE) */
+
 __END_DECLS
 
 #endif /* !defined(_STRINGS_H_) */