Implementing the quest size feature (#122).
Detecting fullscreen resolutions depending on the quest size (#122).
Merge branch 'master' into quest_size

Conflicts:
	ChangeLog
Continuing the video manager (#122).
Continuing the quest size and video modes work. Compiles but not tested.
Implement the intermediate surface workaround properly (#220).

- No more surface allocation at each redraw.
- Ability to enable or disable the workaround at compilation time.
Fix windowed_scale2x initialization.
Fix parsing the quest size string.
Sorry
Fix computation of video mode sizes (#122).

Windowed modes and non-wide fullscreen modes are okay now.
Remove a wrong assertion and fix fullscreen_scale2x size.
Improve detection of wide resolutions by returning only wide ones :)
Fullscreen: stretch 320x240 to 640x480 if SDL does not list it (#122).

(In Solarus < 1.1, 320x240 was always stretched to 640x480 in
fullscreen.)
Show a precise warning if the quest does not support your favorite size.