We don't have any user merge extension here and there's no plan to install it, so I'd just decline this request. User:Sveinki has less than 500 edits; User:Sveinn í Felli is older, has an email address and was used recently. If you just stop using "Sveinki", you'll be fine. I can block and/or rename the account you don't want to use and you can place a redirect from one username from the other. We can also recover the password of either account if you lost it and the email address doesn't work.