Enhanced: make more use of cached vehikel_basis_t::weg and vehikel_basis_t::gr.
Enhanced: avoid time consuming float32e8_t::set_value(nom,denom) methods.
Enhanced: save conversions of integer constants to float32e8_t.
Enhanced: replace fahr[0] with front(), which now returns fahr->begin().
Enhanced: replace some loops over fahr[i] with added convoi_t::const_iterator
Removed: unused code
Enhanced: new objlist_t::iterator makes grund_t::get_weg() 25% faster.
The sum of all enhancements of this weekend made convoi_t::sync_step() 10% faster.
Merge branch '112.5-merge' of https://github.com/jamespetts/simutrans-experimental.git into 112.5-merge
Fixed: merge artefacts