Stop Emacs and return to superior process. You can resume later.
If `cannot-suspend' is non-nil, or if the system doesn't support job
control, run a subshell instead.
If optional arg STUFFSTRING is non-nil, its characters are stuffed
to be read as terminal input by Emacs's parent, after suspension.
Before suspending, run the normal hook `suspend-hook'.
After resumption run the normal hook `suspend-resume-hook'.
Some operating systems cannot stop the Emacs process and resume it later.
On such systems, Emacs starts a subshell instead of suspending.
(fn &optional STUFFSTRING)