* src/twaalgos/dupexp.cc, src/twaalgos/dupexp.hh: Rename to...
* src/twaalgos/copy.cc, src/twaalgos/copy.hh: ... these.
Get rid of dupexp_bfs, rename dupexp_dfs as copy, and add
an option to preserve named states.
* src/twaalgos/Makefile.am, src/tests/dupexp.test,
src/tests/ikwiad.cc, src/tests/sccsimpl.test,
src/twa/twagraph.hh, src/twaalgos/dot.cc,
src/twaalgos/stutter.cc, wrap/python/spot_impl.i: Adjust.
* NEWS: Mention this change.