NTFS: Fix several occurences of a bug where we would perform 'var & ~const'

      with a 64-bit variable and a int, i.e. 32-bit, constant.  This causes
      the higher order 32-bits of the 64-bit variable to be zeroed.  To fix
      this cast the 'const' to the same 64-bit type as 'var'.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>