getaddrinfo(): when providing hints, make sure we use addrconfig/v4mapped.

getaddrinfo(): when providing hints, make sure we use addrconfig/v4mapped.

if no hints were specified, getaddrinfo() will assume ai_flags as
AI_ADDRCONFIG | AI_V4MAPPED, which only reports useful results based
on what system supports. For instance AI_ADDRCONFIG will only return
IPv4 if IPv4 address exists, likewise IPv6 will only be returned if
IPv6 address is configured, avoiding these to be tried and error for
most local networks where such address could not be used. AI_V4MAPPED
will map IPv4 address over IPv6 if no IPv4 was found.