MDEV-19275 Provide SQL service to plugins.

SQL service added.
It provides the limited set of client library functions
to be used by plugin.

libservices/sql_service.c

@@ -0,0 +1,19 @@
+
+/* Copyright (c) 2018, Monty Program Ab
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; version 2 of the License.
+
+  This program is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
+*/
+
+#include <service_versions.h>
+SERVICE_VERSION sql_service= (void*)VERSION_sql_service;