Patch from Stephen Tweedie

"In looking at the fix for the ext3 Orlov double-accounting bug, I
 noticed a change to the sb->s_dir_count accounting, restoring a
 missing s_dir_count++ when we allocate a new directory.

 However, I can't find anywhere in the code where we decrement this
 again on directory deletion, neither in ext2 nor in ext3, in 2.4 nor
 in 2.5."

Locking is via lock_super().