(state_ptr_equal, state_ptr_hash): New functors.
* src/tgba/statebdd.hh, src/tgba/statebdd.cc (state_bdd::hash):
New method.
* src/tgba/tgbaexplicit.hh, src/tgba/tgbaexplicit.cc
(state_explicit::hash): New method.
(ns_map, sn_map): Use Sgi::hash_map instead of std::map.
* src/tgba/tgbaproduct.hh, src/tgba/tgbaproduct.cc
(state_product::hash): New method.
* src/tgba/tgbatba.cc (state_tba_proxy::hash): New method.
* src/tgbaalgos/lbtt.cc (acp_seen, todo_set, seen_map): Redefine
using Sgi::hash_map or Sgi::hash_set.
(lbtt_reachable): Don't erase a key that is pointed to by an
iterator.
* src/tgbaalgos/reachiter.cc
(tgba_reachable_iterator::~tgba_reachable_iterator): Likewise.
* src/tgbaalgos/magic.cc (magic_search::~magic_search()): Likewise.
* src/tgbaalgos/magic.hh (hash_type): Redefine using Sgi::hash_map.
* src/tgbaalgos/reachiter.hh (seen_map): Redefine using Sgi::hash_map.
* iface/gspn/gspn.cc (state_gspn::hash): New method.
* src/misc/hash.hh (string_hash): New functor.
