implement all DLL exports (as TODOs)

Now we can use our own compiled LEGO1.LIB rather than one generated from the original. Also implements a script that tests them to help ensure future commits don't break them.

LEGO1/mxvariabletable.cpp

@@ -0,0 +1,20 @@
+#include "mxvariabletable.h"
+
+// OFFSET: LEGO1 0x100b73a0
+void MxVariableTable::SetVariable(const char *key, const char *value)
+{
+  // TODO
+}
+
+// OFFSET: LEGO1 0x100b7740
+void MxVariableTable::SetVariable(MxVariable *var)
+{
+  // TODO
+}
+
+// OFFSET: LEGO1 0x100b78f0
+const char *MxVariableTable::GetVariable(const char *key)
+{
+  // TODO
+  return 0;
+}