Fix Opting-Out of Linking with Photos Framework (facebookarchive#1519)

Source/ASMultiplexImageNode.h

@@ -9,7 +9,14 @@
 
 #import <AsyncDisplayKit/ASImageNode.h>
 #import <AsyncDisplayKit/ASImageProtocols.h>
+
+#if AS_USE_PHOTOS
 #import <Photos/Photos.h>
+#else
+@class PHAsset;
+@class PHImageManager;
+@class PHImageRequestOptions;
+#endif
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -125,10 +132,11 @@ typedef NS_ENUM(NSUInteger, ASMultiplexImageNodeErrorCode) {
 
 /**
  * @abstract The image manager that this image node should use when requesting images from the Photos framework. If this is `nil` (the default), then `PHImageManager.defaultManager` is used.
- 
+
  * @see `+[NSURL URLWithAssetLocalIdentifier:targetSize:contentMode:options:]` below.
  */
 @property (nullable, nonatomic) PHImageManager *imageManager API_AVAILABLE(ios(8.0), tvos(10.0));
+
 @end
 
 
@@ -249,6 +257,9 @@ didFinishDownloadingImageWithIdentifier:(ASImageIdentifier)imageIdentifier
 @end
 
 #pragma mark -
+
+#if AS_USE_PHOTOS
+
 @interface NSURL (ASPhotosFrameworkURLs)
 
 /**
@@ -266,4 +277,6 @@ didFinishDownloadingImageWithIdentifier:(ASImageIdentifier)imageIdentifier
 
 @end
 
+#endif
+
 NS_ASSUME_NONNULL_END