Made access to the VFS archive cache more 'atomic'. (Previously, it could happen that an archive was marked in use by one thread while being 'checked up' by another.)
Made access to the VFS archive cache more 'atomic'.
(Previously, it could happen that an archive was marked in use by one thread while being 'checked up' by another.)

git-svn-id: 28d9401aa571d5108e51b194aae6f24ca5964c06@33358 8cc4aa7f-3514-0410-904f-f2cc9021211c

crystalspace/CS,crystalspace/CS,crystalspace/CS,crystalspace/CS,crystalspace/CS,crystalspace/CS,crystalspace/CS,crystalspace/CS