Add strongswan (#1330)

package/strongswan/Makefile

package/strongswan/files/ipsec.button

package/strongswan/files/ipsec.conf

package/strongswan/files/ipsec.config

package/strongswan/files/ipsec.cron

package/strongswan/files/ipsec.iface

package/strongswan/files/ipsec.init

package/strongswan/patches/100-ar-fixes.patch

package/strongswan/patches/110-make-ipsec.patch

package/strongswan/patches/120-make-pluto.patch

package/strongswan/patches/130-make-starter.patch

package/strongswan/patches/200-wakeup-showstatus.patch

package/strongswan/patches/210-updown.patch

package/strongswan/patches/300-openwrt.patch

package/strongswan/patches/310-make-ipsec-alg.patch

package/strongswan/patches/320-no-modprobe.patch

package/strongswan/patches/350-make-programs.patch