Configure: fixed static nginx build with OpenSSL (ticket #903). 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.