Changelist for r6461

Fixes :

• crash when loading the level 'The Kerosene Crush'
• munster lander now behave properly
• crash when completing a mission and no more mission are available to unlock
• crash when buying a machine gun that has no separate magazine (ex python)
• possible fix for crash in hostage init
• possible fix for crash with pickup rendering

Tweaks :

• massive tweak to damage output of the munster lander to make it.. hard