Changed objectVersion to 54 so Xcode 12 can load the projects (thanks @Wohlstand!)

Xcode/SDL/SDL.xcodeproj/project.pbxproj

@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 55;
+	objectVersion = 54;
 	objects = {
 
 /* Begin PBXAggregateTarget section */

Xcode/SDLTest/SDLTest.xcodeproj/project.pbxproj

@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 55;
+	objectVersion = 54;
 	objects = {
 
 /* Begin PBXAggregateTarget section */