Reworked the fmtext format to use in-line formatting. Characters used
for formatting are part of Unicode Supplemental Private Area-B, or
Plane 16.
fmtext no longer need 5x the text space to store formatting
information, though they are harder to change at arbitrary
points. This was something we hardly ever did anyhow, and we can still
do everything we need to do.
fmtext keeps a pair of colors and a char for default attributes to be
applied when necessary.
Searching is now done inline at owl_fmtext_waddstr() rather than
specifying a section of the string to be reversed.
This probably still needs some cleanup and more comments, but it
works.