May take days...but it'll do the job. Require lots of memory.
To check your progress, open developer console on Firefox or Chrome. Was going to add a feature to display progress on the webpage, but memory increased by 400%.
Version 1.4 stores giveaway links already scanned using GM_set. This way, after the first scan, or subsequent scans should be faster. There appears to be some errors newly introduced in this version, but does not seem to affect anything. Will fix in future versions.