Massive spaces->tabs and trailing whitespace cleanup, hopefully for the last
time now I've configured emacs to make them displayed in really annoying
colours...
Cleanup by moving various (mostly horrible) little bits handling UTF-8 grid
data into functions in a new file, grid-utf8.c, and use sizeof intead of
UTF8_DATA.
Also nuke trailing whitespace from tmux.1, reminded by jmc.
