A simple way to detect at runtime if we're running in UIKit legacy mode or the new "flat" variant. Written for our PDF iOS SDK (http://pspdfkit.com), where the precompiled binary needs to detect at runtime in what variant it's running. Want more stuff like that? Follow me on Twitter: http://twitter.com/steipete

	// Taken from http://PSPDFKit.com. This snippet is under public domain.
	#define UIKitVersionNumber_iOS_7_0 0xB57
	BOOL PSPDFIsUIKitFlatMode(void) {
	static BOOL isUIKitFlatMode = NO;
	static dispatch_once_t onceToken;
	dispatch_once(&onceToken, ^{
	// We get the modern UIKit if system is running >= iOS 7 and we were linked with >= SDK 7.
	if (kCFCoreFoundationVersionNumber >= kCFCoreFoundationVersionNumber_iOS_7_0) {
	isUIKitFlatMode = (NSVersionOfLinkTimeLibrary("UIKit") >> 16) >= UIKitVersionNumber_iOS_7_0;
	}
	});
	return isUIKitFlatMode;
	}