bug#42350: 26.3; C-c C-c in R console buffer causes Control key to get "stuck"

[Eli Zaretskii]

> From: Mark Seeto <markseeto@gmail.com>
> Date: Thu, 16 Jul 2020 19:45:23 +1000
> Cc: 42350@debbugs.gnu.org
> 
> Start Python:
> M-x run-python <return>
> 
> Go to the Python console buffer:
> C-x o
> 
> Using the right Control key:
> C-c C-c <return>

Thanks.  It turned out you don't need Python or R to reproduce this:
any process run via comint.el will cause the same problem, for example
"M-x gdb".  The problem was in how we restored the status of the Ctrl
key after interrupting a subprocess; I've now fixed that on the
emacs-27 branch.