This cleans up constructors so fields are initialized in the same order they
are declared in. This makes it trivial to spot accidentally uninitialized
fields.

This fixes a minor argument parsing bug when the mount path isn't set, but
fortunately argv[argc] is NULL and we wanted to set it to NULL anyway.

This prevents excessively large block sizes from being used.

This improves inode value range checks in the fsmarshall code. Inode 0 is
not a valid inode. The new code for this is also simpler.

This prevents creating links with names larger than 255 bytes.

This adds a check to ensure inodes don't overflow the hardlink count.

This ensures the dirent filetype is only set if supported.