* src/tgba/state.hh (state_ptr_less_than::operator()): Make it const.
* src/tgba/tgbaproduct.cc: Include string.hh.
* src/ltlast/multop.hh (multop::add, multop::add_sorted): Do
not use qualified names in declarations.
* m4/gccwarn.m4 (CF_GXX_WARNINGS): Fix GXX test.
* src/ltlenv/defaultenv.hh, src/ltlenv/defaultenv.cc,
src/ltlenv/environment.hh: Add virtual destructors.