Forgotten RELEASE_CRUNCH hack for mppe.c.

This fix is for "make release" and "make boot.flp".

usr.sbin/ppp/Makefile

@@ -91,8 +91,8 @@ DPADD+= ${LIBNETGRAPH}
 # We must create these objects because crunchgen will link them,
 # and we don't want any unused symbols to spoil the final link.
 CFLAGS+=-DNONAT -DNORADIUS -DNOI4B -DNOSUID
-OBJS+=	chap_ms.o id.o nat_cmd.o radius.o
-chap_ms.o id.o nat_cmd.o radius.o:
+OBJS+=	chap_ms.o mppe.o id.o nat_cmd.o radius.o
+chap_ms.o mppe.o id.o nat_cmd.o radius.o:
 	>null_${.PREFIX}.c
 	cc -c -o ${.TARGET} null_${.PREFIX}.c
 .endif