c/user: register() prevent DB error if username is non-ascii
c/user: register() prevent DB error if username is non-ascii

The DB col is set to ascii_general_ci so if the username doesn't pass
the charset check we shouldn't even bother query the db because that can
trigger a collation error (utf-8 vs ascii).

Signed-off-by: Florian Pritz <753f544d2d01592750fb4bd29251b78abcfc8ecd@xinu.at>

jreinert/filebin,jreinert/filebin,jreinert/filebin,jreinert/filebin,jreinert/filebin,Bluewind/filebin,Bluewind/filebin,jreinert/filebin,Bluewind/filebin,Bluewind/filebin,Bluewind/filebin