mbuf: remove rte_ctrlmbuf

mbuf: remove rte_ctrlmbuf

The initial role of rte_ctrlmbuf is to carry generic messages (data
pointer + data length) but it's not used by the DPDK or it applications.
Keeping it implies:
  - loosing 1 byte in the rte_mbuf structure
  - having some dead code rte_mbuf.[ch]

This patch removes this feature. Thanks to it, it is now possible to
simplify the rte_mbuf structure by merging the rte_pktmbuf structure
in it. This is done in next commit.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
* Updated patch to HEAD.
* Modified patch to retain the old function names for ctrl mbufs as
  macros. This helps with app compatibility, and allows the concept
  of a control mbuf to be reintroduced via a single-bit flag in
  a future change.
* Updated the packet framework ip_pipeline example application to
  work following this change.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>