They’re faster, even if they’re used outside of ARC. Use dispatch functions to spin off new threads. Update the Binary Delta tool's class to be better.
Delta updates code uses libxar, which is only available in 10.5+, and Sparkle framework fails to load on 10.4 because of it. Instead of having hard dependency on libxar, Sparkle now links with it weakly and checks for its availability at runtime. This required bumping Xcode project compatibility to 3.2 to get weak linking support. With this change, delta updates are still not supported on 10.4, but Sparkle runs there again and just ignores the deltas. This should be good enough given 10.4's age and shrinking user base.
…ly install the delta updates.