Merge pull request #2832 from michaelmou/fix_symbol_mac

Fix macOS 10.10 symbol definition of NSURLSessionTaskPriorityHigh

SDWebImage/Core/SDWebImageDownloaderOperation.m

@@ -11,7 +11,7 @@
 #import "SDInternalMacros.h"
 
 // iOS 8 Foundation.framework extern these symbol but the define is in CFNetwork.framework. We just fix this without import CFNetwork.framework
-#if (__IPHONE_OS_VERSION_MIN_REQUIRED && __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0)
+#if ((__IPHONE_OS_VERSION_MIN_REQUIRED && __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0) || (__MAC_OS_X_VERSION_MIN_REQUIRED && __MAC_OS_X_VERSION_MIN_REQUIRED < __MAC_10_11))
 const float NSURLSessionTaskPriorityHigh = 0.75;
 const float NSURLSessionTaskPriorityDefault = 0.5;
 const float NSURLSessionTaskPriorityLow = 0.25;