Add read and write support for FreeArc's version of the .arc format. Its file type optimized compression is up to 5 times faster than others in certain situations. While it does not always have a clear advantage over others, it is unbeatable in certain situations. For example when compressing the output of Kaspersky's offline updater, I found it to be at least 5 times faster than 7-zip for the same file size.