External structures are now identical regardless of mail SSL module
compiled in or not.

External structures are now identical regardless of stream SSL module
compiled in or not.

With this change it is now possible to load modules compiled without
the "--with-http_ssl_module" configure option into nginx binary compiled
with it, and vice versa (if a module doesn't use ssl-specific functions),
assuming both use the "--with-compat" option.

With this change it is now possible to load modules compiled without
the "--with-file-aio" configure option into nginx binary compiled with it,
and vice versa, assuming both use the "--with-compat" option.

With this change it is now possible to load modules compiled without
the "--with-threads" configure option into nginx binary compiled with it,
and vice versa (if a module does not use thread-specific functions),
assuming both use the "--with-compat" option.

It is used at least by SOAP (M-POST method, defined by RFC 2774) and
by WebDAV versioning (VERSION-CONTROL and BASELINE-CONTROL methods,
defined by RFC 3253).

Linux can return AF_UNIX sockaddrs with partially filled sun_path,
resulting in spurious comparison failures and failed binary upgrades.
Added proper checking of the lengths provided.

Reported by Jan Seda,
http://mailman.nginx.org/pipermail/nginx-devel/2016-September/008832.html.

Previously, user access bits were always set to "rw" unconditionally,
even with "user:r" explicitly specified.  With this change we only add
default user access bits (0600) if they weren't set explicitly.

Duplicate processing was possible if the address set by realip was
listed in set_realip_from, and there was an internal redirect so module
context was cleared.  This resulted in exactly the same address being set,
so this wasn't a problem before the $realip_remote_addr variable was
introduced, though now results in incorrect $realip_remote_addr being
picked.

Fix is to use ngx_http_realip_get_module_ctx() to look up module context
even if it was cleared.  Additionally, the order of checks was switched to
check the configuration first as it looks more effective.

Made sure to set the variable length only after successful SNI parsing.