Implement dataflow for record patterns

Strategy: there is now a regular flow step from an instance-of LHS / switch expr to the pattern, 0 or more read steps corresponding to record pattern destructors, and then finally a normal SSA def/use step connecting the binding patterns to their first uses.

java/ql/lib/config/semmlecode.dbscheme

@@ -576,6 +576,10 @@ lambdaKind(
   int bodyKind: int ref
 );
 
+isCanonicalConstr(
+  int constructorid: @constructor ref
+);
+
 arrays(
   unique int id: @array,
   string nodeName: string ref,