Bug 188976: avoid calculating the difference of two unsigned integer if the difference is really a negative number.  Thanks to Rick Swift for the patch.
Bug 188976: avoid calculating the difference of two unsigned integer if
the difference is really a negative number.  Thanks to Rick Swift for the
patch.

thespooler/nspr,thespooler/nspr,thespooler/nspr,thespooler/nspr,thespooler/nspr