Internals: Add UASSERT_OBJ macro to replace hand-done ifs. No functional change intended.

This makes it easier to filter out correctly zero code-coverage lines.

src/V3Clean.cpp

@@ -78,7 +78,8 @@ private:
             } else {
                 nodep->dtypeChgWidth(width, nodep->widthMin());
                 AstNodeDType* new_dtypep2 = nodep->dtypep();
-                if (new_dtypep2 == old_dtypep) nodep->v3fatalSrc("Dtype didn't change when width changed");
+                UASSERT_OBJ(new_dtypep2 != old_dtypep, nodep,
+                            "Dtype didn't change when width changed");
                 old_dtypep->user3p(new_dtypep2);  // Remember for next time
             }
         }