feature: force trigger

[varesa]

Every now and then I'd like to see the state the lines are in. For example on some agilent oscilloscopes there is a button labeled "Force trigger", that causes the device to trigger ignoring the trigger settings. This should not be too hard to implement?

For example I'm debugging a I2C device, with the trigger set on SCL transition from high to low. Sometimes I'd like to know if the lines are high (idle) or down (stuck) without messing with my trigger settings or using other instruments