- IOAddress test renamed
 - flipped isV6() with !isV4() in perfdhcp/test_control.cc

 - SocketCallbackContainer is now SocketCallbackInfoContainer
 - test callback is now quiet

 - SessionCallback renamed to SocketCallback
 - Removed references in comments to session
 - removed unused names string in receive{4,6}
 - extended unit-test to check that unregistered callback is not
   triggered
 - Implemented similar tests for receive6()
 - Fixed a bug that was revealed by those new unit-tests :)

Conflicts:
	src/lib/dns/tests/rrset_unittest.cc

The merge conflict resolution was reviewed by Shane on Jabber.

Also, removed spurious whitespaces from 743.

Conflicts:
	src/bin/dhcp6/dhcp6_srv.cc

   references the stored default_user.csv file so lettuce tests run.
   Change reviewed by jreed in jabber.

code review by jreed

Implements use of dhcp-ddns configuration parameters in b10-dhcp4.

This fixes a bug which occurs if parseHeader() is called separately from
fromWire().