It was only used to share implementation between IconButton and Link.
However, there was only one non-trivial method, handleTS(), and that
method used a different code path for each use case: doubleClick was
always false for IconButton and always true for Link. So the total
amount of code was actually reduced by eliminating this code sharing.
The main motivation for this split is that I can now freely refactor
Link without having to worry about IconButton.
Each part of the code deals with either Links or IconButtons, but
not both: the base class is only used to share implementation and
not interface. Make this explicit by doing private inheritance.
The code still has a lot of overlap with the other methods of Link and
LinkApp, but at least it is in the same place now.
Since this was the last outside use, setIconPath() could be declared
as 'protected'.
LinkApp now calls its launch method via the delegate mechanism instead of
via an overridden virtual method. This should make it easier to move the
launch method out of LinkApp and into the GMenu2X main class.
