Cache the escape sequences we've seen when checking for those which
don't take any visual space when writing the prompt or similar strings.
This reduces the cost of determining the true cost of such strings by a
full order of magnitude if they include lots of such escape sequences.
Periodically sort the cached escape sequence lengths based on feedback
from cache hits so that we're always checking for the most likely
sequence lengths first.
Also cache the prompt layouts to avoid doing the calculations if the
prompt doesn't change.
Fixes#3793
Remove the "make iwyu" build target. Move the functionality into the
recently introduced lint.fish script. Fix a lot, but not all, of the
include-what-you-use errors. Specifically, it fixes all of the IWYU errors
on my OS X server but only removes some of them on my Ubuntu 14.04 server.
Fixes#2957
This change moves source files into a src/ directory,
and puts object files into an obj/ directory. The Makefile
and xcode project are updated accordingly.
Fixes#1866