Made env. sound falloff configurable thru engine/misc.txt using
key sound_falloff, the default settings value is 15 but can now
changed.
Fixes deletion of saved games to use game_prefix if used.
This closes issue #406
Merge pull request #405 from hean01/master

A few fixes.
Merge branch 'master' of https://github.com/clintbellanger/flare-engine