This fixes two things.

On the one hand we have the old "cruft" mount option, that sometimes was
enabled automatically, for ridiculously large files or CDROMs.  But what
was ridiculous ten years ago, no longer is.  So, only decide that
something is cruft when the user said so. 

On the other hand, sometimes we get negative sizes.  That is caused by
assignments inode->i_size = isonum_733(), where the latter was declared
integer.  I made it unsigned int, as the standard also does.

(Someone with problems replied:
  >> Could you test the below?
  > Ok I did, the patch seems to work great!  Thanks!
)