collaboration diagrams.
* doc/mainpage.dox: Typo.

* src/tgba/state.hh (state::as_bdd): Delete.
* src/tgba/tgbaproduct.hh (state_bdd_product): Inherit from state,
not state_bdd.
(state_bdd_product::state_bdd_product): Adjust.
* src/tgba/tgbaproduct.cc (state_bdd_product::state_bdd_product):
Adjust.

* src/tgba/succiter.hh (tgba_bdd_succ_iterator::done):
Mark as const.
* src/tgba/succiterconcrete.cc
(tgba_succ_iterator_concrete::done): Likewise.
* src/tgba/succiterconcrete.hh
(tgba_succ_iterator_concrete::done): Likewise.
* src/tgba/tgbaexplicit.cc
(tgba_explicit_succ_iterator::done): Likewise.
* src/tgba/tgbaexplicit.hh
(tgba_explicit_succ_iterator::done): Likewise.
* src/tgba/tgbaproduct.cc
(tgba_product_succ_iterator::done): Likewise.
* src/tgba/tgbaproduct.hh
(tgba_product_succ_iterator::done): Likewise.
* src/tgba/tgbatranslateproxy.hh
(tgba_translate_proxy_succ_iterator::done): Likewise.
* src/tgba/tgbatranslateproxy.cc
(tgba_translate_proxy_succ_iterator::done): Likewise.

* src/tgba/succiterconcrete.cc
(tgba_succ_iterator_concrete::next): Call bdd_satoneset
on data_.varandnext_set.  The previous implementation
was wrong for GFa.
* src/tgba/tgbabddcoredata.hh: Declare varandnext_set.
* src/tgba/tgbabddcoredata.cc: Handle varandnext_set.