correct return value check

Signed-off-by: Etienne Basset <etienne.basset@ensta.org>
remove french comments in get_subnet_or_ip
copy comments to .h

Signed-off-by: Etienne Basset <etienne.basset@ensta.org>
harden str2mask
remove uneeded spaces in iptools.c

Signed-off-by: Etienne Basset <etienne.basset@ensta.org>
code cleanup iptools.c

Signed-off-by: Etienne Basset <etienne.basset@ensta.org>
forbid %s in subnettools echo
%s derefence a pointer so that can be dangerous

Signed-off-by: Etienne Basset <etienne.basset@ensta.org>
clean ups in subnet_tool.c

Signed-off-by: Etienne Basset <etienne.basset@ensta.org>