Return void properly, else clang aborts with
* tok_io.c:231:6: error: non-void function 'do_control' should return a value [-Wreturn-type]
See also: https://bugs.gentoo.org/show_bug.cgi?id=523096

--- dev86-0.16.21/unproto/tok_io.c
+++ dev86-0.16.21/unproto/tok_io.c
@@ -189,7 +189,7 @@
 
 /* do_control - parse control line */
 
-static int do_control()
+static void do_control()
 {
     struct token *t;
     int     line;