Add new functions for RPC-Port

Add new functions for RPC-Port

After this patch is applied, the rpc-port uses unix domain socket
instead of socket pair. When the stub calls aul_rpc_port_create(), AMD
creates the socket. And then, AMD sends the socket fd to the stub.
The stub process uses the received socket fd for managing the connection.

Adds:
 - aul_rpc_port_usr_prepare_stub()
 - aul_rpc_port_create()
 - aul_rpc_port_usr_create()
 - aul_rpc_port_destroy()
 - aul_rpc_port_usr_destroy()
 - aul_rpc_port_add_watch()
 - aul_rpc_port_usr_add_watch()
 - aul_rpc_port_remove_watch()
 - aul_rpc_port_exist()
 - aul_rpc_port_usr_exist()
 - aul_rpc_port_get_path()
 - aul_rpc_port_usr_get_path()

Change-Id: I71a7bdaf7ba50e456c6662c524bf3d833030e4e6
Signed-off-by: Hwankyu Jhun <h.jhun@samsung.com>