Update to 20080615.
Add DESTDIR support.

changes since wide-dhcpv6-20070507
[common]
- fixed several memory-related problems
- fixed a improper handling of a domain-name ending with '.'
- fixed a replay-check failure
- fixed a typo in manuals

[dhcp6s]
- fixed a lifetime calculation failure in RENEW/REBIND process
  for stateful-address.
- fixed a bug that dhcp6s cannot accept a relayed
  request message with authentication option.

(jakllsch)