Milestone Avahi 0.6.9

This release fixes some bugs and includes minor enhancements.

• Don't allow registration of address records with invalid host names
• Clean up argument validity checking for AvahiHostNameResolver? and AvahiAddressResolver?
• Fix Avahi builds without DBUS

This release is backwards compatible with Avahi 0.6, 0.6.1, 0.6.2, 0.6.3, 0.6.4, 0.6.5, 0.6.6, 0.6.7 and 0.6.8.