Some more const string fixes.
diff --git a/lib/sockunion.c b/lib/sockunion.c
index 587b324..eb29ced 100644
--- a/lib/sockunion.c
+++ b/lib/sockunion.c
@@ -133,7 +133,7 @@
 }
 
 int
-str2sockunion (char *str, union sockunion *su)
+str2sockunion (const char *str, union sockunion *su)
 {
   int ret;