SSL: RSA data type is deprecated in OpenSSL 3.0.

The only consumer is a callback function for SSL_CTX_set_tmp_rsa_callback()
deprecated in OpenSSL 1.1.0.  Now the function is conditionally compiled too.
diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index 2a0d005..7c262d9 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -1116,6 +1116,8 @@
 }
 
 
+#if (OPENSSL_VERSION_NUMBER < 0x10100001L && !defined LIBRESSL_VERSION_NUMBER)
+
 RSA *
 ngx_ssl_rsa512_key_callback(ngx_ssl_conn_t *ssl_conn, int is_export,
     int key_length)
@@ -1126,7 +1128,7 @@
         return NULL;
     }
 
-#if (OPENSSL_VERSION_NUMBER < 0x10100003L && !defined OPENSSL_NO_DEPRECATED)
+#ifndef OPENSSL_NO_DEPRECATED
 
     if (key == NULL) {
         key = RSA_generate_key(512, RSA_F4, NULL, NULL);
@@ -1137,6 +1139,8 @@
     return key;
 }
 
+#endif
+
 
 ngx_array_t *
 ngx_ssl_read_password_file(ngx_conf_t *cf, ngx_str_t *file)
diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
index a415b4b..7fb4c5f 100644
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -196,8 +196,10 @@
 ngx_int_t ngx_ssl_ocsp_get_status(ngx_connection_t *c, const char **s);
 void ngx_ssl_ocsp_cleanup(ngx_connection_t *c);
 ngx_int_t ngx_ssl_ocsp_cache_init(ngx_shm_zone_t *shm_zone, void *data);
+#if (OPENSSL_VERSION_NUMBER < 0x10100001L && !defined LIBRESSL_VERSION_NUMBER)
 RSA *ngx_ssl_rsa512_key_callback(ngx_ssl_conn_t *ssl_conn, int is_export,
     int key_length);
+#endif
 ngx_array_t *ngx_ssl_read_password_file(ngx_conf_t *cf, ngx_str_t *file);
 ngx_array_t *ngx_ssl_preserve_passwords(ngx_conf_t *cf,
     ngx_array_t *passwords);