let `cnd_signal()` take `.frequency` arg

[maxheld83]

I want to separately construct conditions with *_cnd() and signal them with cnd_signal(). As far as I can see, it is currently not possible to set a .frequency (and id) for a condition thus signaled, though this is possible when creating and signaling in one go with, say inform().

There may be a good reason for this, so apologies if this doesn't make sense.

I was hoping for a .frequency (and id) argument to cnd_signal(), but could not find that.

It makes sense to me that you'd set .frequency in cnd_signal(), not *_cnd(), since cnd_signal() is the place where you emit the side-effect. (Also, setting .frequency in *.cnd() could get quite thorny if these conditions are chained together).