Use 'vluint64_t' for SystemC instead of (same sized) 'uint64' for MSVC++.

src/V3AstNodes.cpp

@@ -185,7 +185,7 @@ string AstVar::cPubArgType(bool named, bool forReturn) const {
     } else if (isWide()) {
 	arg += "uint32_t";  // []'s added later
     } else {
-	arg += "uint64_t";
+	arg += "vluint64_t";
     }
     if (isWide()) {
 	if (forReturn) v3error("Unsupported: Public functions with >64 bit outputs; make an output of a public task instead");
@@ -237,7 +237,7 @@ string AstVar::scType() const {
 	    return "uint32_t";
 	}
     } else {
-	return "uint64_t";
+	return "vluint64_t";
     }
 }