This fixes a bug when wrapping on a word with style changes inside it,
where the copied style would be different depending on the width of the
terminal.
Never split a codepoint, don't set wrapping point unless we're not
already wrapping, wrap on any unicode whitespace, only clear rest of
line if still on the same line...
Still missing: split scrolling and preserving a blank on reflow either
from resize or ignore toggling.
Anecdata: on one of my instances of catgirl, RAM usage of the previous
release was ~30M, RAM usage of this commit was ~12M.
C. McEnroe