Updated: project files
Removed: useless "convoi_t &convoy = *this;" from calc_acceleration()
Enhanced: 50% faster hole_ab() by caching halthandles.
Optimized: 6 times faster haltestelle_t::verbinde_fabriken() by reducing the number of fabrik_t::get_fab() calls.
Merge branch '112.5-merge' of git://github.com/BerndGabriel/simutrans-experimental.git into 112.5-merge
Fixed: missing buttons in map_frame.cpp
Merge branch '112.5-merge' of git://github.com/BerndGabriel/simutrans-experimental.git into 112.5-merge