class library: jitlib-patterns: refactoring: pattern proxies should behave more like their source pattern

In the pattern system, the role of a non-pattern object is ambiguous: in some cases, when used as an input of a pattern, it will return itself endlessly (e.g. in a Pbind value). In other cases (e.g. as an element of a Pseq list), they are used only once and give way to the next element. Pattern proxies should actually behave the same dependent on their input. This means that asStream and embedInStream have to be implemented slightly differently. A new method "streamArg" is responsible for this.

Pattern proxies should actually behave the same dependent on their input. This means that asStream and embedInStream have to be implemented slightly differently: all pattern proxies now behave to asStream and embedInStream like their respective source objects. E.g. Pdefn(\x, 800); Pbindef(\freq, Pdefn(\x)) will loop 800, while Pseq([Pdefn(\x), 900]) will return first 800, then 900.

One minor change: pass node proxy to event when playing event stream