Make message methods static and make message object private.
Make game_message struct private.
Put add_msg() in the global namespace, because its called 2300 times.
Fix offset passed to message display method from log viewer window.
Fix bad road connections near bridges and rivers

Esp. when those are 2 bridges next to each other
Merge branch 'bridge_fix' of https://github.com/Wuzzy2/Cataclysm-DDA into doublemerge