Fixes to testpid() for Windows. Handle processes that no longer exist and processes that belong to another user. Enables the lock breaking changes from d314a89fa4f1 and subsequently "fixes" the left over locks reported in bug 112.

#!/bin/sh

hg init

echo "Is there an error message when trying to diff non-existing files?"
hg diff not found

echo "Is there an error message when trying to add non-existing files?"
hg add not found