fix "ss -p" segfaults

fix "ss -p" segfaults

I've updated Jose's patch to make it slightly simpler (eg: calloc instead
of malloc+memset), and ported it to 4.2.0 which requires it as well, and
attached it to this e-mail.

I can confirm that with this patch 4.1.1 doesn't segfault on me anymore.
The commit message should be reworked I guess though everything's in it
and I didn't want to modify his description.

Can it be merged as-is or should I reword the commit message and reference
Jose as the fix reporter ? We should not let this bug live forever.

From: "j.ps@openmailbox.org" <j.ps@openmailbox.org>

Essentially all that is needed to get rid of this issue is the
addition of:

    memset(u, 0, sizeof(*u));

after:

    if (!(u = malloc(sizeof(*u))))
            break;

Also patched some other situations (strcpy and sprintf uses) that
potentially produce the same results.

Signed-off-by: Jose P Santos <j.ps@openmailbox.org>
[ wt: made Jose's patch slightly simpler, all credits to him for the diag ]
Signed-off-by: Willy Tarreau <w@1wt.eu>