[Texmacs-dev] Braces

[Joris van der Hoeven]

I finally managed to implement wide braces today.
The implementation is very hacky; the font stuff really
has to be reorganized too sometime; I will not further
increase the complexity until this reorganization by the way.

Anyway, the idea is to provide a new construction on
bitmap characters: stretch a given column of the character
horizontally by a certain amount of space. This allows me
to produce wide braces, but also a variety of wide arrows.
The same thing has been implemented for vertical stretching.

I also implemented braces as wide accents. They are available
through the menus. Keyboard shortcuts, LaTeX conversions,
translations, etc. have still to be implemented.