Brought back 'smooth view'. Took some hours to untangle it all,
code was spread all over, instead of localized in 1 call. Tsk!
Still not perfect, but at least more in control. For the hackers;
check void smooth_view() in view3d_view.c, here all 3d view
stuff should be handled, so it can optionally use animating.
For the users: 'smooth view' now plays at a maximum of 30 hz,
and doesn't block anymore. So even slow animated views remain
responsive if you press many numpad keys.
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