[xfrout3] removed libxfr.  we don't need this broken stuff anymore.
[xfrout3] removed lib/xfr from ./configure target
[xfrout3] removed all remaining reference to lib-xfr from auth.
[xfrout3] integrated statistics tests on unixdom sockets in xfroutsrv test.

(New)XfroutServer was slightly modified to catch bind() failure.
[xfrout3] cleanup: get rid of UnixSockServer and old XfroutServer

also removed any now-unsed stuff: definitions, functions, imports, and tests.
[xfrout3] cleanup: removed now-unused log messages.

XFROUT_EXITING was moved to the new main function.
Merge pull request #34 from bundy-dns/xfrout3

Xfrout3 cleanup: remove now-unused defs for xfrout