Scroll-lock key does not work

[NonerKao]

As title.

Expected Behavior

Once the scroll-lock key is enabled (often shown as the 3rd LED behind the number pad),
the terminal should stop refreshing the output from running jobs,
so that the user can examine temporary log easily.

Current Behavior

The scroll-lock key has no effect.

System Information

• Distribution & Version: Arch
• Kernel: 4.13.6
• Qt Version: 5.9.2
• libqtxdg Version: 2.0.0
• qtermwidget Version: 0.8.0
• lxqt-build-tools Version: 0.4.0
• Package version: 0.8.0

[yan12125]

As a side note, the standard keys to stop/start scrolling is Ctrl+S and Ctrl+Q. It should be useful to allow other keys.

TODO: call TerminalDisplay::outputSuspended when specific keys are hit. That should be customizable in keytab files.