Merge pull request #152 from fdelapena/master

Don't require JPEG library in ./configure
Add Screen Tone and fix ToneBlit (saturation still looks partly wrong)
Implement flash screen
Fix segfault because Screen drawable was deleted while wrong Graphic was on stack.
update automake file
Change z (was affecting battle animations)
add some documentation
fix flash (again)
Don't reset tint on map change
Create flash surface once on first use
Refactor weather effect to only render in Graphics::Update instead of Player::Update -> Should be faster (and more correct)
Reenable weather effect for all devices
Fix fog opacity
Change opacity of rain, looks better imho
Fix drawing order (first to last): Weather -> Screen Effects -> Battle Anim -> MsgBox
Create weather surface on first use
Don't clear weather on map change
Adjust pan speed to correct value
add doc
Adjust drawing order again. Some tiles (star type?) were drawn over rain and screen.
Correct order is: Tiles -> Weather -> Screen Effects -> Pictures -> Battle Anim -> MsgBox