Avoid an implicit int to improve compatibility with future compilers.
Borrowed from https://src.fedoraproject.org/rpms/foobillard/blob/f41/f/foobillard-c99.patch

--- a/src/billmove.c
+++ b/src/billmove.c
@@ -409,7 +409,7 @@ void record_move_log_event( enum event_type event,
 }
 
 
-int my_rand(nr)
+int my_rand(int nr)
 {
     return rand()%nr;
 }