Make libxcap compilable on FreeBSD, particularly:
o always include <time.h> before libxml's headers, since apparently they
expect time_t to be defined;
o reorder includes, so that system ones are includes first;
o add appropriate -I/-L into Makefile (quick hack). It would be better if
those libs were using main ser's Makefile* infrastructure, so that it's
possible to re-use LOCALBASE.