Checking updates from the menu was giving feedback when no update was
found, but checking updates from the Check now button in the options was
only giving feedback if a new version was found. Now it also tell us when
ScummVM is up to date.
This was leading to an unhandled exception within Sparkle code
which was hanging the application. This feature is good only for development
purposes, as convenient users are supposed to run ScummVM from the
supplied bundle.
This patch was provided by fingolfin (see patch #3582260). It replaces
use of methods introduced in MacOS X 10.4 with methods that exists
since MacOS X 10.0.