* lib/vcsn/dyn/context-parser.cc, lib/vcsn/dyn/signature-printer.cc,
* vcsn/dyn/context-parser.hh, vcsn/labelset/nullableset.hh: Now
the displayed name for nullableset _is_ nullableset, no longer lan.
'lan' is still accepted in input though.

* tests/python/automaton.dir/lan_char_z.daut,
* tests/python/automaton.dir/lan_char_z.out.gv,
* tests/python/automaton.dir/lan_char_z.tex.gv,
* tests/python/automaton.py,
* tests/python/compose.dir/result.gv,
* tests/python/compose.py,
* tests/python/context.py,
* tests/python/insplit.py,
* tests/python/prefix.dir/aut1-subword.gv,
* tests/python/prefix.dir/aut2-subword.gv,
* tests/python/prefix.dir/aut3-subword.gv,
* tests/python/prefix.dir/aut4-subword.gv,
* tests/python/product.py,
* tests/python/proper.py,
* tests/python/thompson.py:
Adjust.