The test_case_template.hpp header is deprecated in Boost, and the
latest Boost version is now throwing warnings during the build.
In Boost 1.59 (at least), this header is included transitively by the main
Boost test header, so this header is not needed by any supported Boost
version.
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.