Merge pull request #1 from SupSuper/master

Backporting
Merge remote-tracking branch 'upstream/master'

Backport.
fix arrow colour
don't recover ammo from weapons that use themselves as ammo
adjust selection arrow
Fix units ignoring walk orders
Replace scaling options with SDL2-provided ones.

Now you can make your game look terrible or slightly less terrible! Yay!
More pinch-to-zoom goodness on geoscape
Merge remote-tracking branch 'upstream/master' into experimental
fix soldiers with a jesus complex
add some missing data

and remove some redundant stuff
fix cancel button
why do math when a const int will do just as well

the math was off anyway.
Merge remote-tracking branch 'upstream/master' into experimental

Conflicts:
	src/Menu/OptionsBaseState.cpp
Merge remote-tracking branch 'upstream/master' into experimental
Place the text input window higher so that it won't get overlapped by on-screen keyboard
Add preliminary texture overlays (to be eventually used for a mobile interface)
Fix aliens not blowing enough shit up.
Fix explosiveEfficacy logic error
Merge pull request #847 from DarkDefender/grenade_fix

Fix explosiveEfficacy logic error