Several fixes to 7DRL entry

My initial 7DRL submission contained a few problems that hampered gameplay considerably. Therefore I felt an update was necessary. The changelist is below:

• Fix a playthrough stopper if player is out of ammo and the target is still alive
• Add SHIFT to aim, so trackpads can be used to play the game, since those tend to not register holding down both LMB and RMB
• Add toggle between integer scaling (crisp pixels) and smooth scaling (full use of window area) and default to the latter
• Disable the audio subsystem, there is no sound anyway and I had a report it was bugging out