#26 /mode nick +x doesn't work for setting user mode

[Tara McGrew]

Users who are familiar with other clients expect to be
able to set their user mode with /mode <nick> <flags>.
The /mode command should at least show an informative
message when used in this way, instead of being sent
straight through to the server and causing an
unexpected error message.

The user mode syntax that ViRC has used for 8 years is
/umode <flags>.