(install-arch-indep): Don't recursively change perms of

(install-arch-indep): Don't recursively change perms of
site-lisp and infodir.  There may be non-Emacs files in here, and the
files supplied by Emacs are all handled explicitly already.  (Bug#3800)
(mkdir): Set umask to world-readable before creating directories.
mkinstalldirs already checks if dirs exist, don't duplicate this test.