Notes on implementing CL:STREAM correctly

Boot to CLOS representation of ANSI-STREAM via (hypothetical) stream.lisp.

Optional load, as CLOS is expensive.

Possibly subclass AnsiStream.java, but this may not be necessary (inner static class of Stream.java?)

Follow [design document][1] to "thunk back up" to proper encoding, always, via restarts.

[1]: ​http://trac.common-lisp.net/armedbear/browser/trunk/abcl/doc/design/streams/design.rst