memchan

I'm not sure if this is a bug in Tcl or a bug in
memchan, but:

The TIP82 change in the signature of Tcl_DriverSeekProc
breaks stub-compatibility. If memchan is compiled
against 8.3 headers
and loaded into an 8.4a5 interp, all hell breaks loose.

Would it be possible for Tcl_Seek() to check the
Tcl_ChannelTypeVersion field and act accordingly,
passing a 'long' instead of a Tcl_WideInt if the
channel driver has a pre-8.3 version?

Alternately, the current stub table entry for
Tcl_RegisterChannel() could be
changed to point to Tcl_RegisterChannelOld() and a new
one allocated for
the new Tcl_RegisterChannel() (much like what was done
for Tcl_Seek
and Tcl_Tell). (I think I like this option better).

This really ought to get straightened out before 8.4
goes final.