The reduces a little bit of WX dependency, and makes
the timing code a bit more type-safe.
Also adds a more testable interface for the accelerated
zoom controller.
This is done to avoid a big chunk of conditionally-compiled code
in the middle of the event function.
Also separates the zoom logic from the WX_VIEW_CONTROLS object
and isolates it in a separate class behind a clearer interface.
Add some simple tests for sane steps on GTK+3-sized scroll
steps.
Seth Hillbrand
jean-pierre charras
John Beard