BUG/MEDIUM: checks: agent doesn't get the response if server does not closes

The agent refrains from reading the server's response until the server
closes, but if the server waits for the client to close, the response
is never read. Let's try to fetch a whole line before deciding to wait
more.
BUG/MEDIUM: map: Bad map file parser

There is a mix-up between input type of the data and input type of the
map file. This mix-up causes that all pattern matching function based
on "string"  (reg, beg, end, ...) don't run.

This bug came with commit d5f624d (MEDIUM: sample: add the "map" converter),
no backport is needed.
CLEANUP/MINOR: standard: use the system define INET6_ADDRSTRLEN in place of MAX_IP6_LEN
BUG/MEDIUM: sample: conversion from str to ipv6 may read data past end

Applying inet_pton() to input contents is not reliable because the
function requires a zero-terminated string. While inet_pton() will
stop when contents do not match an IPv6 address anymore, it could
theorically read past the end of a buffer if the data to be converted
was at the end of a buffer (this cannot happen right now thanks to
the reserve at the end of the buffer). At least the conversion does
not work.

Fix this by using buf2ip6() instead, which copies the string into a
padded aread.

This bug came with recent commit b805f71 (MEDIUM: sample: let the
cast functions set their output type), no backport is needed.