Attached is an updated version of the patch, which avoids
several of the problems mentioned, by using a different lock file name
on MS-Windows.  Non-MS-Windows uses .#FILE symlinks as before;
MS-Windows uses .#-FILE regular files.  This avoids clashes
between the two approaches.  It also means MS-Windows ignores
non-MS-Windows locks and vice versa, but given all the
inherent incompatibilities involved this may be the best that
we can do reliably.