Avoid implicit ints, to improve compatibility with future compilers
which may rejected them by default.

diff --git a/null.c b/null.c
index 435025ded8ecb0b7..7ba7ed2bcfbb8715 100644
--- a/null.c
+++ b/null.c
@@ -179,6 +179,7 @@ int f;
 }
 
 int minmaxfb(f,fb)
+int f,fb;
 {
   int i,j=-1;