When no more directory entries are available in the existing
cluster(s) of a directory on FAT32, we allocate an
extra cluster.
Make sure to zero out that new cluster, as disk checking utilities
may not stop reading when reaching an end of directory marker but
read the rest of cluster as well.
So there must not be any garbage data from a previously deleted file
in the sector there.
Also add checks to prevent getting in an endless loop on
encoutering circular "next cluster" references.
Floris Bos
a403df4385