- added a dummy struct named '_' to define global variables. This can only be used internally.

This method was chosen because it avoids adding variable declarations to the global namespace which would have required a lot more work while polluting the grammar.
This way the global variables can be handled by a small bit of special coding in the struct generator.

src/menu/menudef.cpp

@@ -67,6 +67,8 @@ PClass *DefaultOptionMenuClass;
 
 void I_BuildALDeviceList(FOptionValues *opt);
 
+DEFINE_GLOBAL_NAMED(OptionSettings, OptionMenuSettings)
+
 DEFINE_ACTION_FUNCTION(FOptionValues, GetCount)
 {
 	PARAM_PROLOGUE;