pipeline: add new functions for action handlers

pipeline: add new functions for action handlers

Two new pipeline API functions have been added to the library. The packet
hijack API function can be called by any input/output port or table action
handler to remove selected packets from the burst of packets read from one
of the pipeline input ports and then either send these packets out through
any pipeline output port or drop them.

Another packet drop API function can be used by the pipeline action
handlers (port in/out, table) to drop the packets selected using packet
mask. This function updates the drop statistics counters correctly.

Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>