AppleTalk address parsing
atalk_aton(char * cp, struct at_addr * ata);
routine converts an ASCII representation of an AppleTalk address to a format appropriate for system calls. Acceptable ASCII representations include both hex and base 10, in triples or doubles. For instance, the address `0x1f6b.77' has a network part of `8043' and a node part of `119'. This same address could be written `8043.119', `31.107.119', or `0x1f.6b.77'. If the address is in hex and the first digit is one of `A-F', a leading `0x' is redundant.