OpenDingux, od-input.c: Squash opposing directions even if they come from mixed sources (d-pad and analog nub).
OpenDingux: Add persistent per-game settings. Dingoo A320: Fix a segmentation fault in the Display Settings menu, caused by the lack of a NULL sentinel entry.
OpenDingux: Save settings only when they are changed in a submenu.

This will create per-game setting files only for games for which the user has made overrides. It will also reduce the number of erase cycles counted against the internal flash storage in the user's device.
OpenDingux, English and French manuals: Update with documentation on per-game settings.