* src/misc/escape.hh, src/misc/escape.cc (escape_latex): New function.
* src/ltlvisit/tostring.cc: Escape atomic proposition in LaTeX output.
* wrap/python/spot.py: Make it easy to output formulas in different
syntaxes. Also allow the AST to be shown.
* wrap/python/spot_impl.i: Catch std::runtime_error.
* wrap/python/tests/formulas.ipynb: New file.
* wrap/python/tests/Makefile.am: Add it.
