[CMD] Improve how the command prompt displays when one presses Ctrl-C/break after having pressed ENTER, or after a command has been run.

base/shell/cmd/cmdinput.c

@@ -453,8 +453,14 @@ BOOL ReadCommand(LPTSTR str, INT maxlen)
                 if ((ir.Event.KeyEvent.dwControlKeyState &
                     (RIGHT_CTRL_PRESSED|LEFT_CTRL_PRESSED)))
                 {
-                    /* A CTRL-C.  Don't clear the the command line,
-                     * but return an empty string in str. */
+                    /* Ignore the Ctrl-C key event if it has already been handled */
+                    if (!bCtrlBreak)
+                        break;
+
+                    /*
+                     * A Ctrl-C. Do not clear the command line,
+                     * but return an empty string in str.
+                     */
                     str[0] = _T('\0');
                     curx = orgx;
                     cury = orgy;