Improve E_UNSUPPORTED warning messages (#7329)

src/V3Timing.cpp

@@ -1046,7 +1046,9 @@ class TimingControlVisitor final : public VNVisitor {
         // Do not allow waiting on local named events, as they get enqueued for clearing, but can
         // go out of scope before that happens
         if (!nodep->sentreep()) {
-            nodep->v3warn(E_UNSUPPORTED, "Unsupported: no sense equation (@*)");
+            nodep->v3warn(E_UNSUPPORTED,
+                         "Unsupported: Event control with implicit sensitivity (@*)"
+                         " in this context; use an explicit sensitivity list instead");
             VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
             return;
         }