MediaWiki – customize standard deletion reasons

This is quite hard to find when you don’t have sysop rights on any wiki, and thus can’t the the delete reason drop-down list to be able to search for it. So here they are, just for you , the pages you want to edit if you want to add custom reasons for deletion in the drop-down menu of the delete page:
For pages, the reasons are in MediaWiki:Deletereason-dropdown
For files, the reasons are in MediaWiki:Filedelete-reason-dropdown
This was checked in MediaWiki 1.12.0, but is probably the same in any version which contains these drop-down lists.