Revert "Made possible to specify where to dump the contents when loading a ".pck" file"

This reverts commit ffcfd9c8ea.

This was not so useful as is due to the way dependency paths are stored
in scenes and resources.

core/io/file_access_zip.h

@@ -74,7 +74,7 @@ public:
 
 	bool file_exists(String p_name) const;
 
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files, const String &p_destination = "");
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files);
 	FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file);
 
 	static ZipArchive *get_singleton();