- consolidated I_FatalError functions

This also removes the handling from thr Posix backend and will not compile on non-Windows.

src/d_main.cpp

@@ -2290,6 +2290,42 @@ void I_Error(const char *error, ...)
 	throw CRecoverableError(errortext);
 }
 
+//==========================================================================
+//
+// I_FatalError
+//
+// Throw an error that will end the game.
+//
+//==========================================================================
+extern FILE *Logfile;
+
+void I_FatalError(const char *error, ...)
+{
+	static bool alreadyThrown = false;
+	gameisdead = true;
+
+	if (!alreadyThrown)		// ignore all but the first message -- killough
+	{
+		alreadyThrown = true;
+		char errortext[MAX_ERRORTEXT];
+		va_list argptr;
+		va_start(argptr, error);
+		myvsnprintf(errortext, MAX_ERRORTEXT, error, argptr);
+		va_end(argptr);
+		I_DebugPrint(errortext);
+
+		// Record error to log (if logging)
+		if (Logfile)
+		{
+			fprintf(Logfile, "\n**** DIED WITH FATAL ERROR:\n%s\n", errortext);
+			fflush(Logfile);
+		}
+
+		throw CFatalError(errortext);
+	}
+	std::terminate(); // recursive I_FatalErrors must immediately terminate.
+}
+
 //==========================================================================
 //
 // I_Quit