add regtest for route aggregation
-fix netcsv_GW_handle to not interpret IPv6 address as comment
-modify aggregate_route to handle different GW
add a small 'is_link_local' helper
add reg test for aggregation with a route where
- gw6 is the same
- but gw6 is a link local address and device is different
teach is_equal_gw to compare device if GW IPv6 adresses are link-local
add a compress argument to 'subnet2str'
will use it to change the IPv6 address display
add a command-line  option for setting IPv6 compression level
add a 'compress_level' arg to print_subnet_file & friends;
convert all calls
Initial support of dynamic output formating
void print_route_fmt(struct route r, FILE *output, const char *fmt)
where fmt is a 'printf like'  string :
 %I or %1I or %0I for IP
 %m for mask
 %D for device
 %g for gateway
 %C for comment