[Click] Click forward declaration error

[Daniel Pall]

This is probably a fairly elementary problem, but how do I fix this
compilation error?

/proj/Chang/tmp/click-1.6.0/linuxmodule/../elements/etherswitch/spantree.cc:205:
error: invalid use of undefined type 'struct EtherSwitch'
/proj/Chang/tmp/click-1.6.0/linuxmodule/../elements/etherswitch/spantree.hh:8:
error: forward declaration of 'struct EtherSwitch'

(Background: we had to modify EtherSwitch to mesh with the custom module
that we wrote as a Click extension...but now spantree doesn't seem to
recognize EtherSwitch.  I assume that this problem could be fixed by somehow
declaring EtherSwitch to spantree...any ideas?)

Thanks,
Dan