strongswan: add missing dependencies

Fix the following build failures by adding the missing dependencies:

Package strongswan-mod-connmark is missing dependencies for the following libraries:
libip4tc.so.2

Package strongswan-mod-forecast is missing dependencies for the following libraries:
libip4tc.so.2

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

net/strongswan/Makefile

@@ -673,7 +673,7 @@ $(eval $(call BuildPlugin,blowfish,Blowfish crypto,))
 $(eval $(call BuildPlugin,ccm,CCM AEAD wrapper crypto,))
 $(eval $(call BuildPlugin,chapoly,ChaCha20-Poly1305 AEAD crypto,))
 $(eval $(call BuildPlugin,cmac,CMAC crypto,))
-$(eval $(call BuildPlugin,connmark,netfilter connection marking,))
+$(eval $(call BuildPlugin,connmark,netfilter connection marking,+iptables-legacy))
 $(eval $(call BuildPlugin,constraints,advanced X509 constraint checking,))
 $(eval $(call BuildPlugin,coupling,IKEv2 plugin to couple peer certificates permanently to authentication,))
 $(eval $(call BuildPlugin,ctr,Counter Mode wrapper crypto,))
@@ -690,7 +690,7 @@ $(eval $(call BuildPlugin,eap-radius,EAP RADIUS auth,))
 $(eval $(call BuildPlugin,eap-tls,EAP TLS auth,+strongswan-libtls))
 $(eval $(call BuildPlugin,farp,fake arp respsonses,))
 $(eval $(call BuildPlugin,fips-prf,FIPS PRF crypto,+strongswan-mod-sha1))
-$(eval $(call BuildPlugin,forecast,forward multi/broadcast traffic,+kmod-ipt-conntrack-extra))
+$(eval $(call BuildPlugin,forecast,forward multi/broadcast traffic,+iptables-legacy +kmod-ipt-conntrack-extra))
 $(eval $(call BuildPlugin,gcm,GCM AEAD wrapper crypto,))
 $(eval $(call BuildPlugin,gcrypt,libgcrypt,+PACKAGE_strongswan-mod-gcrypt:libgcrypt))
 $(eval $(call BuildPlugin,gmp,libgmp,+PACKAGE_strongswan-mod-gmp:libgmp))