Fix TORQUE_UNUSED for recent versions of MSVC

Since there's now apparently no way to suppress the warning for a
particular variable without adding at least some extra size to the
executable, just turn the warning off in release builds. We leave it on in
debug since it can sometimes help catch bugs, and we don't care about a
little extra code in that configuration.

Engine/source/platform/types.visualc.h

@@ -32,6 +32,16 @@
 typedef signed _int64   S64;
 typedef unsigned _int64 U64;
 
+// The types.h version of TORQUE_UNUSED no longer works for recent versions of MSVC.
+// Since it appears that MS has made this impossible to do in a zero-overhead way,
+// just turn the warning off in release builds.
+#undef TORQUE_UNUSED
+#ifdef TORQUE_DEBUG
+#define TORQUE_UNUSED(var) ((0,0) ? (void)(var) : (void)0)
+#else
+#pragma warning(disable: 4189) // local variable is initialized but not referenced
+#define TORQUE_UNUSED(var) ((void)0)
+#endif
 
 //--------------------------------------
 // Compiler Version