MINOR: standard: Add ipv6 support in the function url2sa().

The function url2sa() converts faster url like http://<ip>:<port> in a
struct sockaddr_storage. This patch add:
 - the https support
 - permit to return the length parsed
 - support IPv6
 - support DNS synchronous resolution only during start of haproxy.

The faster IPv4 convertion way is keeped. IPv6 is slower, because I use
the standard IPv6 parser function.
3 files changed