* lukas/kernel/fix_os_cmd_background_compat/OTP-13741:
  kernel: Use ^D as eot for os:cmd on unix platforms

* raimo/ssl/version-selection/maint-19/OTP-13753:
  Improve version selection

This is needed as doing only an 'exit' will only exit the
program, but any children started in the program that have
stdout/stderr still open will keep the port open until they
terminate. i.e.

    os:cmd("while true; do echo sleep 1; sleep 1; done&").

would block os:cmd forever because the while loop keeps its copies
of stdout/stderr open forever.

It could be argued that this is correct behaviour, and it is
the way it works on windows, but changing this breaks backwards
compatability for os:cmd which is not acceptable.

Change it to { Input :: string() | undefined, Body :: string() }

Conflicts:
	lib/ssl/vsn.mk
	lib/ssl/src/ssl.appup.src