Autosaves a campaign.

local saveId = 1
Campaign_QuickSaveNb(saveId, "M01 %d Mission Start")
Note: the output, in the example above, would be "AutoSave_M01 1 Mission Start".

<sDescription>: raw string or localization ID.
<iId>: if the description contains the string "%d" somewhere within it, then <iId> will be inserted in the place of "%d".

Only works in Campaign mode.
A "game saved" message will be displayed on the screen.
The string "Autosave_" will be always be appended to the beginning of the description.