SSL: fixed build with OPENSSL_NO_DEPRECATED defined. The RSA_generate_key() is marked as deprecated and causes build to fail. On the other hand, replacement function, RSA_generate_key_ex(), requires much more code. Since RSA_generate_key() is only needed for barely usable EXP ciphers, the #ifdef was added instead. Prodded by Piotr Sikora.

--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -656,10 +656,14 @@ ngx_ssl_rsa512_key_callback(ngx_ssl_conn
         return NULL;
     }
 
+#ifndef OPENSSL_NO_DEPRECATED
+
     if (key == NULL) {
         key = RSA_generate_key(512, RSA_F4, NULL, NULL);
     }
 
+#endif
+
     return key;
 }