Too short circuit input propagation delay when clicked

[flandreas]

Circuit inputs can also be toggled by the user with the mouse, if they are part of the top-level circuit. Their default propagation delay of 1 ns is also applied when being clicked by the user. If a circuit input (with attribute "toggle" unset) drives the clock input of a D-flipflop, a very short click/release by the user doesn't trigger the flipflop, because the resulting impulse is too short for the edge detection component of the D-flipflop is implemented in the standard library, especially if the current simulation speed is small.

When being clicked by the user, a circuit input should apply the same propagation delay like a normal switch, something like 1000 ns.