[c-nsp] subrate DS3, pa-mc-2t3+

[Kevin Graham]

> I have an situation where, for testing/demo purposes, we need to nail
> down the bandwidth on both ends of a DS3. 

If you just need to arbitrarily cap it on a whim (i.e. not actually
accomodating a fractionally-provisioned circuit), GTS will be much
easier and more flexible:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/fqcprt4/qcfgts.htm