Renaming “Realname” to “Userdata”

The IRC specification currently calls for a “realname” field. In addition to serving identification purposes, this field is often auto-filled by IRC clients with the IRC client name, as well as being used by the gender spec to carry genders.

This specification proposes calling it “userdata”, at least in user interface. Projects may also want to call it userdata or irc_userdata in code.