Add Lua scripting feature

Add support for running Lua scripts that can manipulate the tty control
lines. Script is activated automatically on connect or manually via in
session key command.

The Lua scripting feature opens up for many posibilities in the future
such as adding expect like functionality to easily and programatically
interact with the connected device.

src/script.h

@@ -0,0 +1,32 @@
+/*
+ * tio - a simple serial terminal I/O tool
+ *
+ * Copyright (c) 2014-2024  Martin Lund
+ *
+ * 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; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * 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 Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#pragma once
+
+enum script_run_t
+{
+    SCRIPT_RUN_ONCE,
+    SCRIPT_RUN_ALWAYS,
+    SCRIPT_RUN_NEVER,
+    SCRIPT_RUN_END,
+};
+
+void script_run(int fd);