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/meson.build

@@ -18,14 +18,27 @@ tio_sources = [
   'rs485.c',
   'timestamp.c',
   'alert.c',
-  'xymodem.c'
+  'xymodem.c',
+  'script.c'
 ]
 
+
+foreach name: ['lua-5.4', 'lua-5.3', 'lua-5.2', 'lua-5.1', 'lua']
+  lua_dep = dependency(name, version: '>=5.1', required: false)
+  if lua_dep.found()
+    break
+  endif
+endforeach
+if not lua_dep.found()
+  error('Lua could not be found!')
+endif
+
 tio_dep = [
   dependency('threads', required: true),
   dependency('inih', required: true,
                      fallback : ['libinih', 'inih_dep'],
-                     default_options: ['default_library=static', 'distro_install=false'])
+                     default_options: ['default_library=static', 'distro_install=false']),
+  lua_dep
 ]
 
 tio_c_args = ['-Wno-unused-result']