Add integer() to CommonSubExpression.isSkipCase, ticket:4224

Author: rfranke

Compiler/BackEnd/CommonSubExpression.mo

@@ -855,6 +855,7 @@ algorithm
     case DAE.CALL(path=Absyn.IDENT("semiLinear")) then true;
     case DAE.CALL(path=Absyn.IDENT("homotopy")) then true;
     case DAE.CALL(path=Absyn.IDENT("reinit")) then true;
+    case DAE.CALL(path=Absyn.IDENT("integer")) then true;
     case DAE.CALL(path=Absyn.IDENT("String")) then true;
     case DAE.CALL(path=Absyn.IDENT("firstTick")) then true;
     case DAE.CALL(path=Absyn.IDENT("interval")) then true;