Move check for access of context for nested class from backend into frontend.

dmd/declaration.h

@@ -636,7 +636,12 @@ struct FuncDeclaration : Declaration
     FuncDeclaration *isFuncDeclaration() { return this; }
 
     // llvmdc stuff
+
+    // vars declared in this function that nested funcs reference
+    // is this is not empty, nestedFrameRef is set and these VarDecls
+    // probably have nestedref set too, see VarDeclaration::checkNestedReference
     std::set<VarDeclaration*> nestedVars;
+
     std::string intrinsicName;
 
     bool isIntrinsic();