Major code audit and clean-up for GC (Synergy, 584f867)

Have audited the entire codebase for GC problems and in the process have cleaned up a lot of the code (Objective-C 2.0 properties, shorter allocation patterns, fast enumeration and so forth). In all inserted just over 1200 lines and deleted over 2000.

Signed-off-by: Greg Hurrell <greg@hurrell.net>