iNew: TimeSlide in Action Window

iNew: TimeSlide in Action Window

Usage: press Tkey, and you can proportionally squeeze or stretch the
selected keys, with current mouse position as reference. Only works with
more than 3 keys selected horizontally.

I've remapped the old Tkey (ipo type) to SHIFT+T... might be temporal, I
have an idea for a cool 2D manipulator system that makes it much friendlier
to grab/scale/slide keys all in once.

Also: fix for HOME key in action editor (didn't do Pin), and removed gcc
warnings from jiri's commit in editmesh_add.c