MSVS build: Suppress warning C4244 (possible loss of data)

VC++ is picky about narrowing conversion. Let's ignore it instead of
scattering static_casts.

src/sys/nact.cpp

@@ -302,7 +302,7 @@ void NACT::message()
 		else
 			break;
 	}
-	int len = static_cast<int>(end - begin);
+	int len = end - begin;
 	scenario_addr += len;
 
 	char* buf = (char*)alloca(len + 1);