Changes:
* Split patty_ax25_frame_decode() into the following:
- patty_ax25_frame_decode_address()
- patty_ax25_frame_decode_control()
This allows for look up an established socket for a given address
pair, to determine if an SABME session is in progress,
necessitating modulo-128 control decoding
* Decode I and S N(R), N(S) sequence numbers, poll/final
bits properly in both modulo-8 and modulo-128 mode
* Perform better frame control validation
* Implement the following functions in src/sock.c:
- patty_ax25_sock_send_rr()
- patty_ax25_sock_send_rnr()
- patty_ax25_sock_send_rej()
- patty_ax25_sock_send_srej()
Corresponding functions have been removed from src/server.c
* Implement better functions in src/sock.c for encoding frame
control, with send/receive sequences associated with the socket,
with modulo-128 encoding for SABME sessions
Other changes:
* Move or delete macros from include/patty/ax25/macros.h into
include/patty/ax25.h and include/patty/ax25/frame.h
* Move definitions from include/patty/ax25/proto.h to header file
include/patty/ax25.h
* Perform better bounds checking while decoding frames
* Improve frame control printing in src/print.c; display frame
type names, N(R), (NS) sequence numbers, and poll/final bits
