* Loop play-at-speed and cut preview play-at-speed implemented.
* Shift or ctrl down now affect all relevant buttons, loop or cut preview, normal or at speed, and append-record.
One tricky aspect was that until GetActiveProject() is ready to return non-NULL, ControlToolBar::RegenerateToolsTooltips() cannot get the project's CommandManager, so cannot get the shortcuts. Changed ControlToolBar::RegenerateToolsTooltips() to be public and now call it late in wAudacityProject(). When called before the project is completely instantiated, in the rewritten ControlToolBar::RegenerateToolsTooltips(), it just sets the tooltips to the names without the keys, pretty much as now -- but I don't think users will ever see that because of the subsequent call.
Anyway, did it in a more programmatic way than the previous code, which reduces string literals duplication.
Btw, I changed the start value for the ID_PLAY_BUTTON because the former value of 0 causes FindWindow() to return the toolbar rather than the button -- wxWidgets bug.
Also got rid of some cruft and applied a few WXUNUSED.
