[c-nsp] Bonded T1 Circuits

[Kevin Graham]

> You could do 8 if you use four VWIC-2MFT-T1 cards, which is pretty much

> as high as you'd ever want to go with MLPPP.

With the major caveat that the clock is shared between both ports on a the
VWIC. Even knowing this, it has still bitten us when originally identical
T1's got groomed onto different upstream circuits.

HWIC-4T1/E1 doesn't have this limitation, but is only supported on the 
2821 and up.