BUG/MEDIUM: regex: fix pcre_study error handling

pcre_study() may return NULL even though it succeeded. In this case error is
NULL otherwise error is not NULL. Also see man 3 pcre_study.

Previously a ACL pattern of e.g. ".*" would cause error because pcre_study did
not found anything to speed up matching and returned regex->extra = NULL and
error = NULL which in this case was a false-positive. That happend only when
PCRE_JIT was enabled for HAProxy but libpcre has been built without JIT.

Signed-off-by: Christian Ruppert <c.ruppert@babiel.com>

[wt: this needs to be backported to 1.5 as well]
(cherry picked from commit 955f4613cb457a93bb278e47a9af19bf5479d27d)
BUG/MEDIUM: tcp: don't use SO_ORIGINAL_DST on non-AF_INET sockets

There's an issue when using SO_ORIGINAL_DST to retrieve the original
destination of a connection's address before being translated by
Netfilter's DNAT/REDIRECT or the old TPROXY. SO_ORIGINAL_DST is
able to retrieve an IPv4 address when the original destination was
IPv4 mapped into IPv6. At first glance it's not a big deal, but it
is for logging and for the proxy protocol, because we then have
two different address families for the source and destination. In
this case, the proxy protocol correctly detects the issue and emits
"UNKNOWN".

In order to fix this, we perform getsockname() first, and only if
the address family is AF_INET, then we perform the getsockopt() call.

This fix must be backported to 1.5, and probably even to 1.4 and 1.3.
(cherry picked from commit 5e0d0e046a7a54c6f4349e58f0e850105038a71a)