emacs: fix an auto-save permissions race condition

emacs: fix an auto-save permissions race condition

* fileio.c (auto_saving_dir_umask): New static var.
(Fmake_directory_internal): Use it.
(do_auto_save_make_dir): Set it, instead of invoking chmod after
creating the directory.  The old code temporarily assigns
too-generous permissions to the directory.
(do_auto_save_eh): Clear it.
(Fdo_auto_save): Catch all errrors, not just file errors, so
that the var is always cleared.