Fix building under linux.

I commented out the mouse warping code again. We can fix all the instances
later. Also, I undef'ed some mouse wheel related code and fixed it for sdl2. We
should keep all the upstream behaviour, as sdl2 is the future :)
Smooooother Drag Scroll
Oh, and RMB can be used to DragScroll on minimap, again.
Merge branch 'experimental'

Conflicts:
	src/Battlescape/BattlescapeState.cpp
Fix Quick Load without a quicksave crashing game.
Huh, must've broken something by the merge.
Merge remote-tracking branch 'origin/experimental'

Conflicts:
	src/Battlescape/BattlescapeState.cpp
Fix building on linux, maybe introduce a bug or two.
Attempt to return "black" if palette is not available

(Screen surface, now being a 32-bit surface, doesn't really have a palette. Calling a function to get that palette crashes immediately.)
Resizing the window (by setting its resolution) works again.

Grabbing mouse is commented out and needs further examination.
Merge pull request #843 from fenyo1/smoothDragScroll

Smooooother Drag Scroll
Tweak comboboxes
fix minimap scrolling
fix autoshot centering thing
Get mouse position from events, not from SDL function calls.

(Should assist in dealing with broken drag-scroll and stuff)
Merge remote-tracking branch 'upstream/master' into experimental

Conflicts:
	src/Battlescape/BattlescapeState.cpp
	src/Battlescape/MiniMapState.cpp

Drag-scrolling is now not broken at all and fixed in addition to being smooth! Yay!

Also, I should stop doing that thing with the globe.