Added type param to DVarValue as DMD sometimes overrides the type of the VarDeclaration.

Added support for align(1)/packed structs, other alignments are still ignored.
Fixed some problems with accessing lazy arguments.

gen/structs.h

@@ -66,6 +66,7 @@ struct DUnionIdx
 class DUnion
 {
     std::vector<DUnionField> fields;
+    bool ispacked;
 public:
     DUnion();
     LLConstant* getConst(std::vector<DUnionIdx>& in);