autoreconf may need gettext

E. g. for AC_LIB_PREFIX
Strongswan: use full path to ipsec

This fixes issue:

... charon[6135]: 11[CHD] updown: /bin/sh: ipsec: command not found
Strongswan: updown script uses ip and iptables utilities
Strongswan: preserve PATH
Merge pull request #5440 from ip1981/strongswan

Patches to Strongswan