Cleanup|libcommon: Streaming bytes directly to a File

When streaming directly to a File via the IOStream interface, one
does not need to use FixedByteArray as the operation will replace the
entire contents of the file. Files have built-in metadata about
their size, so size won't be included in the written data as with
Writer.

doomsday/plugins/common/src/g_game.cpp

@@ -3057,7 +3057,7 @@ void G_DoLeaveMap()
             SV_OpenFileForWrite(mapStateData);
             writer_s *writer = SV_NewWriter();
             MapStateWriter().write(writer);
-            outFile << de::FixedByteArray(mapStateData);
+            outFile << mapStateData;
             Writer_Delete(writer);
             SV_CloseFile();