* libiberty.h (ffs): Declare, if necessary.

include/libiberty.h

@@ -138,6 +138,13 @@ extern char *libiberty_concat_ptr;
 
 extern int fdmatch (int fd1, int fd2);
 
+/* Return the position of the first bit set in the argument.  */
+/* Prototypes vary from system to system, so we only provide a
+   prototype on systems where we know that we need it.  */
+#if defined (HAVE_DECL_FFS) && !HAVE_DECL_FFS
+extern int ffs(int);
+#endif
+
 /* Get the working directory.  The result is cached, so don't call
    chdir() between calls to getpwd().  */