Fix MSVC warning. No functional change.

include/verilated.cpp

@@ -377,7 +377,6 @@ void VL_PRINTF_MT(const char* formatp, ...) VL_MT_SAFE {
 }
 
 void VL_FFLUSH_MT() VL_MT_SAFE {
-    va_list ap;
     VerilatedThreadMsgQueue::post(VerilatedMsg{[=]() {  //
         Verilated::runFlushCallbacks();
     }});

src/V3LinkInc.cpp

@@ -307,6 +307,7 @@ class LinkIncVisitor final : public VNVisitor {
                 return new AstSub{nodep->fileline(), lhsp, rhsp};
             case AstAssignCompound::operation::Xor:
                 return new AstXor{nodep->fileline(), lhsp, rhsp};
+            default:;  // Error below  // LCOV_EXCL_LINE
             }
         }
         nodep->v3fatalSrc("Unhandled compound assignment operation");

src/V3Randomize.cpp

@@ -1053,7 +1053,7 @@ class ConstraintExprVisitor final : public VNVisitor {
             nodep->user1(false);
             return;
         }
-        bool anyChild = false;
+        int anyChild = false;  // Used as bool
         if (AstNodeExpr* const cp = VN_CAST(nodep->op1p(), NodeExpr)) {
             propagateUser1InlineRecurse(cp);
             anyChild |= cp->user1();