Merge branch 'master' into feature/wrap

This brings in the multi-window code.

Conflicts:
	.gitignore
	Makefile
	buffer.c
	buffer.h
	motion.c
	ui.c
Fix window_linewrap() off by one
Correct nvlines in window rect calculation
Correct line-wrap drawing where cursor is on the end of the line
Correct line-wrap cursor positioning
Guard against division-by-zero in window_toscreen()

e.g. for thin screens.
Fix linewrapping logic for window_toscreen()

Need to figure out the line-wrap between two lines, not the line-wrap
with a maximum (wrap) of n, which would be more wrong the more wraps
there were.
window_linewrap*() changes - clarify limit vs. list-diff
Line wrapping test on fixed-size terminal