Nerf Aero-Evaporator CBM
Prevent insanely huge log files:

If the previous log file is to big, move it another location (log file name + ".prev").
Than continue logging into a new file.
If the log file reaches critical size again, move it away and override the first log file.
Refine game::debugmon:

Rename to debug_mode, that's what it's called when you toggle it from the debug menu.

Moved it to the debug.{cpp,h} files as it is a debug, not a game feature.

Added a message type m_debug, which is *only* shown when the debug mode is activated.
Replaced "if(debug_mode) { add_msg(); }" with simpler "add_msg(m_debug, ...)"
The message class will handle the display of those messages, or it suppresses them if the debug mode is not activated.

Renamed ACTION_TOGGLE_DEBUGMON to ACTION_TOGGLE_DEBUG_MODE to match the actual action name.
Also renamed the visible name of that action in the key binding menu.
Fix crash from items exploding in fire.

Prevent invalid iterator when the explosion destroys items on the same place as the exploded item.
Merge branch 'evap-nerf' of github.com:Shoes01/Cataclysm-DDA into evap-nerf
Prevent Aero-Evaporator exploit
Forgot to add before committing..
Merge branch 'prevent-debug-message' of https://github.com/BevapDin/Cataclysm-DDA into merge