debian packaging: add mroonga and example engines

debian/dist/Debian/mariadb-server-10.0.files.in

 usr/lib/mysql/plugin/auth_pam.so
 usr/lib/mysql/plugin/auth_socket.so
+usr/lib/mysql/plugin/ha_mroonga.so
 usr/lib/mysql/plugin/ha_sequence.so
 usr/lib/mysql/plugin/ha_sphinx.so
 usr/lib/mysql/plugin/ha_innodb.so

debian/dist/Ubuntu/mariadb-server-10.0.files.in

 usr/lib/mysql/plugin/auth_pam.so
 usr/lib/mysql/plugin/auth_socket.so
+usr/lib/mysql/plugin/ha_mroonga.so
 usr/lib/mysql/plugin/ha_sequence.so
 usr/lib/mysql/plugin/ha_sphinx.so
 usr/lib/mysql/plugin/ha_innodb.so

debian/mariadb-test-10.0.files

@@ -6,6 +6,7 @@ usr/lib/mysql/plugin/qa_auth_client.so
 usr/lib/mysql/plugin/auth_0x0100.so
 usr/lib/mysql/plugin/mypluglib.so
 usr/lib/mysql/plugin/ha_test_sql_discovery.so
+usr/lib/mysql/plugin/ha_example.so
 usr/lib/mysql/plugin/daemon_example.ini
 usr/lib/mysql/plugin/libdaemon_example.so
 usr/lib/mysql/plugin/adt_null.so