Add support for multiple Network backends, stub in GOGNetwork

desktop_version/src/GOGNetwork.c

@@ -0,0 +1,29 @@
+#include <stdint.h>
+
+/* Totally unimplemented right now! */
+
+int32_t GOG_init()
+{
+	return 0;
+}
+
+void GOG_shutdown()
+{
+}
+
+void GOG_update()
+{
+}
+
+void GOG_unlockAchievement(const char *name)
+{
+}
+
+int32_t GOG_getAchievementProgress(const char *name)
+{
+	return 0;
+}
+
+void GOG_setAchievementProgress(const char *name, int32_t stat)
+{
+}