Add cutscene test menu

This allows translators to test all text boxes in the scripts. It
doesn't run the scripts themselves - it only shows the basic appearance
of each text box individually, so context may be lost but it's good to
have a way to see any text boxes that might otherwise not be easily
seen because they require specific circumstances to appear.

desktop_version/src/LocalizationMaint.h

@@ -12,6 +12,9 @@ bool save_roomname_explanation_to_files(bool custom_level, int roomx, int roomy,
 void local_limits_check(void);
 void global_limits_check(void);
 
+void populate_testable_script_ids(void);
+bool populate_cutscene_test(const char* script_id);
+
 } /* namespace loc */
 
 #endif /* LOCALIZATIONMAINT_H */