Enable 64bit VSTs on Linux

* Remove trial-and-error approach of detecting VST's machine types. Read PE
  headers instead.
* Add RemoteVstPlugin64 to AppImage

include/RemotePlugin.h

@@ -854,12 +854,11 @@ protected:
 	}
 
 
+	bool m_failed;
 private:
 	void resizeSharedProcessingMemory();
 
 
-	bool m_failed;
-
 	QProcess m_process;
 	ProcessWatcher m_watcher;