Rename strict-ident, apply to non-identd response

Rename strict-ident, apply to non-identd response

Rename "--oidentd-strict" to "--strict-ident", better representing
what it now does - makes all ident replies strict.

Apply strict ident matching to normal (non-identd-enabled) ident,
too.  This allows strict ident to be enforced on IRC networks that do
not check identd responses.

(Yes, some IRC networks behave this way, expecting your shared user
bouncer to enforce ident.  ZNC allows this, so Quassel probably
should too.  No need to run an ident server for those networks.)

Clean up functions, making them a little more generic.  This also
sets the stage for exposing the strict ident mode to the client later
on.