[master] Added ChangeLog entry 672, for trac# 3086.

ChangeLog

+672.	[func]	tmark
+	Added b10-dhcp-ddnsupdate transaction base class, NameChangeTransaction.
+	This class provides the common structure and methods to implement the state 
+	models described in the DHCP_DDNS design, plus integration with DNSClient 
+	and its callback mechanism for asynchronous IO with the DNS servers.
+	(Trac #3086, git 079b862c9eb21056fdf957e560b8fe7b218441b6)
+
 671.	[func]		dclink,tomek
 	memfile backend now supports getLease4(hwaddr) and getLease4(client-id)
 	methods. Thanks to David Carlier for contributing a patch.