Internals: Rename some non-nodes to avoid Ast prefix. No functional change.

src/V3Depth.cpp

@@ -62,7 +62,7 @@ private:
         // Put assignment before the referencing statement
         AstAssign* const assp = new AstAssign{
             nodep->fileline(), new AstVarRef{nodep->fileline(), varp, VAccess::WRITE}, nodep};
-        AstNRelinker linker2;
+        VNRelinker linker2;
         m_stmtp->unlinkFrBack(&linker2);
         assp->addNext(m_stmtp);
         linker2.relink(assp);