Now checks for which range the data is being written to (direct blocks,
     indirect block, or double indirect blocks), but only writes out properly
     to direct blocks.  If the file is too small, it will extend out the
     file by 32k as needed.
add: UbixFS::vfs_mkdir(): works for all cases except vfs_mkdir("/foo//bar");
     Oh, and it does sub-dirs, too, which is something UbixFS v1 never did. HA!
add: vfs_abstract::vfs_purge()