Synergy 6.0a4 release

Synergy version 6.0a4 is out, containing another fix for a crash (bug #2173). 6.0a2 and 6.0a3 were trying to fix the same crash and each version has gotten a little better; I’m hoping this one is the definitive fix.

See the 6.0a release announcement for more details about what’s new in 6.0.