duplicate variable names are bad.

naming iterators "i" is sooo 2012
fix for large units and falling behaviours
small fixes for floating units.
whoops, should check for things before i call them.
fix software rendering.
turns out we DO need an ammo check there, who knew?
make window resizing optional, and default to false.
Merge branch 'master' of https://github.com/SupSuper/OpenXcom