gh-159072: Clarify Ctrl+C and SIGINT handler behavior

Author: jikekei

Doc/library/msvcrt.rst

@@ -114,6 +114,9 @@ Console I/O
    is not already available, but will not wait for :kbd:`Enter` to be
    pressed. If the pressed key was a special function key, this will
    return ``'\000'`` or ``'\xe0'``; the next call will return the keycode.
+   When pressed while this function is waiting for input, :kbd:`Control-C`
+   can be read as ``b'\x03'`` without invoking the :const:`signal.SIGINT`
+   handler.
 
 
 .. function:: getwch()

PC/clinic/msvcrtmodule.c.h

@@ -228,11 +228,13 @@ Nothing is echoed to the console. This call will block if a keypress is
 not already available, but will not wait for Enter to be pressed. If the
 pressed key was a special function key, this will return '\000' or
 '\xe0'; the next call will return the keycode.
+When pressed while this function is waiting for input, Control-C can be
+read as b'\x03' without invoking the signal.SIGINT handler.
 [clinic start generated code]*/
 
 static int
 msvcrt_getch_impl(PyObject *module)
-/*[clinic end generated code: output=a4e51f0565064a7d input=967463215ff3ab9d]*/
+/*[clinic end generated code: output=a4e51f0565064a7d input=5c91f51ac2355241]*/
 {
     int ch;