SSL: removed export ciphers support.

Export ciphers are forbidden to negotiate in TLS 1.1 and later protocol modes.
They are disabled since OpenSSL 1.0.2g by default unless explicitly configured
with "enable-weak-ssl-ciphers", and completely removed in OpenSSL 1.1.0.
diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index ce2a566..3705f5e 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -863,11 +863,6 @@
         SSL_CTX_set_options(ssl->ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
     }
 
-#if (OPENSSL_VERSION_NUMBER < 0x10100001L && !defined LIBRESSL_VERSION_NUMBER)
-    /* a temporary 512-bit RSA key is required for export versions of MSIE */
-    SSL_CTX_set_tmp_rsa_callback(ssl->ctx, ngx_ssl_rsa512_key_callback);
-#endif
-
     return NGX_OK;
 }
 
@@ -1120,32 +1115,6 @@
 }
 
 
-#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)
-{
-    static RSA  *key;
-
-    if (key_length != 512) {
-        return NULL;
-    }
-
-#ifndef OPENSSL_NO_DEPRECATED
-
-    if (key == NULL) {
-        key = RSA_generate_key(512, RSA_F4, NULL, NULL);
-    }
-
-#endif
-
-    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 81b87d7..68e970b 100644
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -29,7 +29,6 @@
 #include <openssl/ocsp.h>
 #endif
 #include <openssl/rand.h>
-#include <openssl/rsa.h>
 #include <openssl/x509.h>
 #include <openssl/x509v3.h>
 
@@ -208,10 +207,6 @@
 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);