Initial diet for large buffer pools.

This removes howler-size allocs, but doesn't solve all
issues.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Adapt to recent changes on Accelio for_next.

* Accelio options now of opaque type
* RDMA behavior now governed by 2 new options

   IO_OPTNAME_MAX_INLINE_DATA
   XIO_OPTNAME_MAX_INLINE_HEADER

Signed-off-by: Matt Benjamin <matt@linuxbox.com>