Trying FAT32 on a small partition failed to mount because
pmp->pm_Sectors was nonzero. Normally, FAT32 file systems are so
large that the 16-bit pm_Sectors can't hold the size. This is
indicated by setting it to 0 and using only pm_HugeSectors. But at
least old versions of newfs_msdos use the 16-bit field if possible,
and msdosfs supports this except for breaking its own support in the
sanity check. This is quite different from the handling of pm_FATsecs
-- now the 16-bit value is always ignored for FAT32 except for
checking that it is 0, and newfs_msdos doesn't use the 16-bit value
for FAT32.
Submitted by: bde
MFC after: 1 week
48efa33b49