... for functions in final classes.
override is like const -- it's not necessary, but it helps the compiler to
catch mistakes.
There may be some overriding functions not explicitly declared virtual and I did
not identify such cases, in which I might also add override.
... Should have no effect on generated code, except perhaps some slight faster
virtual function calls. Mostly useful as documentation of design intent.
Tried to mark every one of our classes that inherits from another, or is a
base for others, or has abstract virtual functions, and a few others besides.
EXPERIMENTAL_SCRUBBING_BASIC enables middle-click-drag to scrub, or to seek
when shift is down.
EXPERIMENTAL_SCRUBBING_SMOOTH_SCROLL adds middle-double-click-drag to
scrub or (with SHIFT down) to seek while keeping the playhead at the midline
of the track display.
EXPERIMENTAL_SCRUBBING_SCROLL_WHEEL allows control wheel to vary the speed
limit, while scrubbing (not seeking).
All three are enabled in this commit.
Also notice the changes to status bar messages and the Mouse Preferences dialog.
Scrubbing works only in Select and Multi tools.
* 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.
