[Coding style] delete whitespaces
flowgrind: move parse_rpc_address to argparser
flowgrind-stop: allow to use IPv6 RPC adresses

This patch makes use of the parse_rpc_address function to
parse RPC addresses.

Closes #70 (flowgrind-stop does not accept IPv6 addresses)
Closes #159 (flowgrind-stop does not complain, if there is no address given)
flowgrind/flowgrind-stop: use asprintf instead of fixed size buffer
Use free_all() in flowgrind_stop.c and flowgrind.c
Clarify comment on netinet/tcp.h once again
[Coding style] make doxygen comments consistent
Missing includes on FreeBSD