[PATCH] finish iso support

[Duncan Sands]

> But as I told you in a previous mail, this part could be dropped : we 
> just need to be sure that all packets have the same size.

Right, but maybe it is useful to have different buffer sizes for iso
vs bulk.  I don't really know - any thoughts on the matter?  Maybe we
should introduce rcv_buf_iso_packets, but calculate the default value
somehow so it is the same as what you'd get if you'd just used rcv_buf_size
and done the calculation we do now (corrected to be sure all packets have
the same size).

Ciao,

D.