r7: cp_get_ifdefault: (new)

 - added function to return default interface or
    it's address, takes an argument: dev or addr

cp_get_cidr:
 - memoizing CP_ECHO_RETURN and using it only for
    our return value not for our calls
 - made awk processing more efficient
 - added verbosity control through CP_VEROBOSE
 - handled netmask 255.255.255.255 as separate case