Handle deserialization of KnowHOWAttribute.

Turns out that with this, we can now deserialize nqp-mo.pm's blob
successfully!

src/org/perl6/nqp/sixmodel/reprs/KnowHOWAttribute.java

@@ -30,6 +30,8 @@ public SixModelObject deserialize_stub(ThreadContext tc, STable st) {
 
 	public void deserialize_finish(ThreadContext tc, STable st,
 			SerializationReader reader, SixModelObject obj) {
-		throw new RuntimeException("KnowHOWAttribute deserialization NYI");
+		KnowHOWAttributeInstance data = (KnowHOWAttributeInstance)obj;
+		data.name = reader.readStr();
+		data.type = tc.gc.KnowHOW; // Not serialized yet
 	}
 }