Blender Git Loki

When looking into code for centering the Ipo view on the current frame,
it turned out it was already in there (center_currframe), and already
had an event entry in the View menu. It only lacked an actual menu entry.

Added the menu entry, along with hotkey Shift-C. Consistency with other
window types would indicate it should be C-key, but that is already taken
by what's probably an obscure curve edit mode function. With event refactor
in the future, I'm loathe to start changing hotkeys ;)