Added (RTLD_NOW | RTLD_GLOBAL) to dlopen() test.  There is no RTLD_GLOBAL
on FreeBSD 2.2.9.

Added uint32_t test, with fallback to u_int32_t, similar to uint64_t one.
Added fallback to u_int32_t in in_addr_t test.

With these changes it is now possible to compile nginx on FreeBSD 2.2.9
with only few minor warnings (assuming -Wno-error).

Before 7142b04337d6, it was possible to build the OpenSSL library
along with nginx, and link nginx statically with this library
(--with-openssl=DIR --with-ld-opt=-static --with-http_ssl_module).
This was broken on Linux by not adding -ldl after -lcrypto.

The fix also makes it possible to link nginx statically on Linux
with the system OpenSSL library, which never worked before.

It appears that AddressSanitizer in GCC 5 intercepts dlopen() and dlclose()
but not dlsym().

It is more effective, because it doesn't require a separate lseek().

Based on a patch by Piotr Sikora.

When configured, an individual listen socket on a given address is
created for each worker process.  This allows to reduce in-kernel lock
contention on configurations with high accept rates, resulting in better
performance.  As of now it works on Linux and DragonFly BSD.

Note that on Linux incoming connection requests are currently tied up
to a specific listen socket, and if some sockets are closed, connection
requests will be reset, see https://lwn.net/Articles/542629/.  With
nginx, this may happen if the number of worker processes is reduced.
There is no such problem on DragonFly BSD.

Based on previous work by Sepherosa Ziehau and Yingqi Lu.