Fix debug script loader crashing missions

* open_script is now exposed in Script.h, perhaps it should be namespaced
as a static method on CTheScripts? I'm unsure what is preferred.
* I've moved the joypad code out of open_script to prevent buttons held
  down at mission load time from changing the scriptToLoad.

src/control/Script6.cpp

@@ -305,7 +305,11 @@ int8 CRunningScript::ProcessCommands1000To1099(int32 command)
 		CTimer::Suspend();
 		int offset = CTheScripts::MultiScriptArray[ScriptParams[0]];
 		CFileMgr::ChangeDir("\\");
+#ifdef USE_DEBUG_SCRIPT_LOADER
+		int handle = open_script();
+#else
 		int handle = CFileMgr::OpenFile("data\\main.scm", "rb");
+#endif
 		CFileMgr::Seek(handle, offset, 0);
 		CFileMgr::Read(handle, (const char*)&CTheScripts::ScriptSpace[SIZE_MAIN_SCRIPT], SIZE_MISSION_SCRIPT);
 		CFileMgr::CloseFile(handle);