Extended path prefix looks like "\\?\",
and NT object path prefix looks like "\??\".
Strip them only if they are followed by a character
(any character) and a colon (:), indicating that
it's a DOS path with a drive.
Otherwise stripping such prefix might result in a patch
that looks like a relative path.
For example, "\\?\Volume{GUID}\" becomes "Volume{GUID}\",
which is a valid directory name.
Currently it's up to the user to make sense of such paths.
