proper default Windows ACLs, e.g. relevant when the bundle is placed into the root directory of a volume;

--- a/Admin/Windows/Cygwin/isabelle/postinstall	Mon Oct 24 20:13:01 2016 +0200
+++ b/Admin/Windows/Cygwin/isabelle/postinstall	Mon Oct 24 20:52:27 2016 +0200
@@ -7,6 +7,7 @@
 mkpasswd -l >/etc/passwd
 mkgroup -l >/etc/group
 
+find -type d -exec setfacl -m default:user::rwx,default:group::r-x,default:other:r-x '{}' +
 find -type d -exec chmod 755 '{}' +
 find -type f \( -name '*.exe' -o -name '*.dll' \) -exec chmod 755 '{}' +
 find -type f -not -name '*.exe' -not -name '*.dll' -not -name '*.scala' -not -name '*.ML' -not -name '*.thy' -exec chmod 644 '{}' +