cygpath automatically adds the root-local prefix \\?\ automatically
for paths exceeding 260 bytes. However, it does not add the root-local
prefix if the path contains path components invalid in DOS paths, for
instance path components with trailing dots or spaces.
Add the -r option to always add the root-local prefix to the path.
Add the option to the documentation and improve the help text.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
a0527e3786