zpaq: mark decompression as unsafe
zpaq: mark decompression as unsafe

A malicious user can create an archive which results in an infinite
loop when attempting to decompress.

Cloudef/squash,Cloudef/squash,jibsen/squash,quixdb/squash,Cloudef/squash,quixdb/squash,quixdb/squash,jibsen/squash,jibsen/squash