rename/copy score parsing updates.

rename/copy score parsing updates.

Better variant, which handles stuff like "4.5%" and rejects
"192.168.0.1".  Additionally, make sure numbers are unsigned (I'm making
them unsigned long just for the hell of it), to make sure that
artificial wraparound scenarios don't cause harm.

	-hpa

[jc: with this, -M100 changes its meaning back to 10%.  People
wanting to say "pure renames only" should now say -M100% or
-M1.0; sounds a bit like an earthquake, but arguably things are
more consistent this way ;-)]

Signed-off-by: Junio C Hamano <junkio@cox.net>