Copyright-holder and year information is extracted from git log.
git history begins in 2005. So (C) from 1998..2005 is lost. Also some
(C) assignment of commits where the committer didn't use --author.
combines selection related editor properties with the current editor selection.
The related editor properties are:
mouse mode,
zoom setting,
left frame of the canvas,
y origin of the canvas.
Selection state now includes region views (storing the underlying region id)
and time.
This patch also fixes a region mute undo bug.