* spot/twa/acc.cc, spot/twa/acc.hh: Add a LaTeX output for acceptance
conditions.
* spot/twaalgos/dot.cc: Implement the 'x' option and refactor the code
a bit to limit duplication.
* tests/core/dot2tex.test: New test case (requires dot2tex).
* tests/Makefile.am: Add dot2tex.test.
* tests/core/alternating.test, tests/core/readsave.test,
tests/python/automata-io.ipynb: Adjust expected output.
* NEWS, doc/org/oaut.org: Mention the new option.