Fixes the build on newer versions of Xcode (#581)

Author: garrettmoon

Source/Classes/PINDisplayLink.m

@@ -11,6 +11,8 @@
 
 #if SWIFT_PACKAGE
 @import CoreVideo.CVDisplayLink;
+#else
+#import <CoreVideo/CoreVideo.h>
 #endif
 
 @interface PINDisplayLink ()