Add AITrack for better positioning (fixes #23)

Moves in such a way that the target is 8-axis
aligned, so they come into the line of fire.
Fix dogfight positioning and quit in multikill

Dogfight should not terminate just because
all players have died
add ports to readme and add wiki image for gcw0 page (#292)
Add new scream sounds (#39)
Merge pull request #299 from carstene1ns/gcw0_doc

add ports to readme and add wiki image for gcw0 page (#292)
Make screams louder (#39)
Don't play same scream consecutively
Add some leeway to diagonals in AITrack (#23)

Movement near diagonals tended to fluctuate
between horizontal and vertical movement, as
that's the boundary between the two movements.
Instead the AI should move diagonally if the
target is perfectly aligned on the diagonal.
Restore mission complete at start

Fixes exit tiles not being displayed
Add debug setting via --debug option
Don't score for friendly hits
Fix random scream
Add X/Y axis leeway to AITrack
WIP networking
Fix const warning
Fix problems from Xcode analysis