Add LongLink Support to Tar reading

[DannyBoyk]

We have to process some Tar files that contain the LongLink header type. Specially, they contain both a LongLink and a LongName header type for a hard link entry. Currently, SharpCompress will not handle the LongLink header properly and accidentally consume the following block as a file instead of as the long link name, resulting in an empty file named @././LongLink, at least, with the Tar file we are dealing with.