Fix: Match GRF ID conventions and correct version checks

Author: zephyris

baseset/nml/extra/extra-header.pnml

@@ -1,5 +1,6 @@
 grf {
-	grfid: "OGZ\0";
+	//grfid: "OGZ\0";
+	grfid: "\FFOT2"; //Adheres to "\FFOT" base set GRF ID range
 	name: string(STR_GRF_NAME);
 	desc: string(STR_GRF_DESCRIPTION);
 	url: string(STR_GRF_URL);

newgrf/nml/settings/settings-header.pnml

@@ -4,7 +4,7 @@ grf {
 	desc: string(STR_GRF_DESCRIPTION);
 	url:  string(STR_GRF_URL);
 	version: 1;
-	min_compatible_version: 1;
+	min_compatible_version: version_openttd(1, 3, 0);
 	param 1 {
 		param_cursors {
 			name: string(STR_PARAM_CURSOR_NAME);
@@ -49,3 +49,13 @@ grf {
 		}
 	}
 }
+
+if (ttd_platform == PLATFORM_OPENTTD) {
+	if (openttd_version < version_openttd(1, 3, 0)) {
+		error(FATAL, REQUIRES_OPENTTD, "1.3.0");
+	}
+}
+
+if (ttd_platform != PLATFORM_OPENTTD) {
+	error(FATAL, REQUIRES_OPENTTD, "1.3.0");
+}