patch: 11_trau

I improved trau_mux.c. Now it supports not just bridging only. A new function "trau_recv_lchan" is used to link a channel to a call reference of a transaction. (Transactions are used in later patches.) TRAU frames will then be forwarded to the application with the given call reference (in later patches). Also the application can send TRAU frames by using "trau_send_lchan". A new list is introduced in trau_mux.c. (upqueue_entry) All subslots that must be sent to application are listed here. Received TRAU frames are written in the upqueue of application interface, if a call reference is found in the upqueue-list. If an entry is found the ss_entry list, the TRAU frames are bridged as before. The frames have a message type (msg_type), a call reference (callref) and a trau frame (data). The length of trau frame is defined by the content of the c-bits inside the frame. There is no support for ip-access yet. Harald must add this in order to use application interface with ip-access. The bridging with ip-access works as before.