* src/ltlvisit/relabel.cc, src/ltlvisit/relabel.hh: New files.
* src/ltlvisit/Makefile.am: Add them.
* src/ltlvisit/clone.cc (recurse): Don't call clone(), nobody
needs that.  Instead, really recurse.
* src/bin/ltlfilt.cc: Add a --relabel option.
* src/bin/genltl.cc: Relabel formulas if --lbt is used.
* src/sanity/style.test: Tweak detection of i++.