Document compile-time switches here as I'm going to yank them from

if_de.c.

sys/modules/de/Makefile

@@ -5,4 +5,16 @@
 KMOD=	if_de
 SRCS=	if_de.c opt_bdg.h device_if.h bus_if.h pci_if.h
 
+# Compile-time options.
+
+#  Enable debugging:
+#CFLAGS+=	-DTULIP_DEBUG
+
+#  Enable performance statistics:
+#CFLAGS+=	-DTULIP_PERFSTATS
+
+#  Enable the use of a software interrupt to alleviate the occurrence of
+#  interrupt livelock when under heavy load:
+#CFLAGS+=	-DTULIP_USE_SOFTINTR
+
 .include <bsd.kmod.mk>