reload when machine clock is ahead of file-system clock

For me, :reload often seems to treat an out-of-date interpreted module
as up-to-date.  I think this is a consequence of my machine clock
being ahead of my file-system clock.

I believe this behavior results from the use of getClockTime as the
linkableTime for interpreted modules.  It seems more correct to use
the mtime of the source.  In general, it seems best not to compare
local-machine times and file-system times.

        thanks,
        mike