Okay, I have a twee problem here. My code:
// BEGIN_INCLUDE
#include "AdvItems.dm"
#ifdef __MAIN__ // BEGIN_DEMO
#include "Example.dm"
#include "item.dmp"
#endif // END_DEMO
// END_INCLUDE
But, the item.dmp line is moved out of the #ifdef whenever I compile. It is Critical that it be inside the ifdef!
I'll look into this. Note that if you ever want to force manual changes to the .dme file, just put your #includes outside of the "// BEGIN" and "// END" blocks.