When using Step on a function that has a dynamic CALL instruction we
set a Step breakpoint on the call.
When it is hit we determine the destination of the CALL by looking at
registers, set a breakpoint there and continue.
If the Step breakpoint is hit simultaneously with a normal breakpoint
our Step logic will take precedence and the normal breakpoint hit will
be hidden from the user.
Move the Step logic to a breaklet callback so that it does not
interfere with the decision to stop.
