Add an "Interrupt Execution" to the Shell menu, per issue13504, annoyance #3 - "PROBLEM: There’s no obvious way to stop a running program. (Don’t expect them to know Ctrl-C)"

I would like to broaden this to add other missing features to the menus. I have no need for this, but I would like history-next/prev added (to shell, as they only apply there). I never learned them because at first I did not know about them and now it is more bother to select options/configure/keys/scroll-down to find the key binding than to click/return. When I get a new program, I often look through the menus to see what is available, so if things are hidden, how do I find out about them?

Does IDle or tkinter or tk automatically add the key shortcuts?

I notice that some key bindings include lower and upper case, some do not. (History next/prev do not.) Is there a reason to not make all cntl/alt bindings case insensitive, and is there an issue for this?

I was thinking about #12387 about caps lock and shortcuts.

I'm ok with broadening the scope of this issue to include other items. 
If we decide to deprecate running IDLE without a subprocess 
(http://mail.python.org/pipermail/idle-dev/2012-June/003124.html), then 
the history-next/prev would fit nicely under the Shell menu.
> Does IDle or tkinter or tk automatically add the key shortcuts?
IDLE adds the key shortcuts. It's broken for extensions if those 
shortcuts are changed. See Issue6092.

The help.txt file needs to be modified as well. See interrupt_execution.patch.

I've provided a patch which seems to bring this change up to date on Python 3.6.0a4+, however I've only manually tested. Having had a look at the existing idle tests, it wasn't clear to me how I could also provide a test. Any suggestions would be appreciated. I ran a childrens' coding workshop at Kiwi PyCon 2016 in Dunedin, New Zealand using IDLE and one child in fact raised this issue and was unfamiliar with Ctrl-C.

Updated description in idle.rst with a fullstop.

New changeset 9148a2213631 by Terry Jan Reedy in branch '2.7':
Issue #15308: Add 'interrupt execution' (^C) to Shell menu.
https://hg.python.org/cpython/rev/9148a2213631

New changeset 74b84014bc27 by Terry Jan Reedy in branch '3.5':
Issue #15308: Add 'interrupt execution' (^C) to Shell menu.
https://hg.python.org/cpython/rev/74b84014bc27

New changeset 63f6ac38d18d by Terry Jan Reedy in branch 'default':
Merge 3.5 - Issue #15308: Add 'interrupt execution' (^C) to Shell menu.
https://hg.python.org/cpython/rev/63f6ac38d18d