string: declare (but do not define) strerrorname_np and strerrordesc_np

Provide declarations for these functions; maybe we'll provide an
implementation someday.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

newlib/libc/include/string.h

@@ -149,6 +149,10 @@ int	__xpg_strerror_r (int, char *, size_t);
 #  define strerror_r __xpg_strerror_r
 # endif
 #endif
+#if __GNU_VISIBLE
+const char *strerrorname_np(int errnum);
+const char *strerrordesc_np(int errnum);
+#endif
 #if __BSD_VISIBLE
 size_t   strlcat (char *, const char *, size_t);
 #endif