Latex backend:
1. Eliminated all parasytic vspaces.
2. Parametrized vertical spaces for syntax and rules. So far they are all set to 0.
3. Improved rendering of anonymous vars.
4. Improved rendering of rule attributes.
5. Implemented automatic line breaking after a rewrite.
6. Added support for high angular brackets.
7. Improved rendering of rewrites, committed a more compact version of rewrite that I used for POPL paper.

Remaining problems:
1. There are still some overfull hbox warnings because of the heavy use of minipages.