Actually the FEATURE() macro is defined on sys/sysctl.h.

Pointyhat to:	loos

sys/geom/uzip/g_uzip.c

@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/malloc.h>
+#include <sys/sysctl.h>
 #include <sys/systm.h>
 
 #include <geom/geom.h>