teach print_route_fmt about newlines and tabs
FIX : wrong outbuf size
-add 'output_fmt' config file option
-add a 'fmt' option
modify calls to fprintf_subnet_file by fprintf_subnet_file_fmt
increase output_fmt so we can print fuuuuuunnnnny things
add a regtest for a strange FMT : HELLO my mask is %m my prefix is %I ma GW est %G, et je te dit '%C'
add files associated to this test