CONTRIB: merge ip6range with iprange

No need to have two separate sub-projects doing the same thing, let's
merge them.
diff --git a/contrib/iprange/Makefile b/contrib/iprange/Makefile
index b3c72ed..13598d8 100644
--- a/contrib/iprange/Makefile
+++ b/contrib/iprange/Makefile
@@ -1,8 +1,8 @@
-CC       = gcc
+CC       = cc
 OPTIMIZE = -O3
 LDFLAGS  = -s
 
-OBJS     = iprange
+OBJS     = iprange ip6range
 
 all: $(OBJS)