Milestone Avahi 0.6.20

This is a bugfix release and contains a fix for a low risk security vulnerability.

• Fix a local DoS vulnerability, where an assert() could be hit by passing empty TXT data over D-Bus to the Avahi daemon. (Low Risk)
• Solaris/dbm portability fixes
• Close all open file descriptors when daemonizing. Is generally safer and fixes a few issues with broken init systems of several distributions.
• avahi-autoipd: allow passing the path of the action script on the command line.
• Several minor build fixes and other cleanups

This release is backwards compatible with Avahi 0.6.x with x < 20.