Bump SDK requirement macro

Sources/VLC for iOS-Prefix.pch

@@ -12,8 +12,8 @@
 
 #import <Availability.h>
 
-#ifndef __IPHONE_7_0
-#error "This project uses features only available in iOS SDK 7.0 and later."
+#ifndef __IPHONE_8_2
+#error "This project uses features only available in iOS SDK 8.2 and later."
 #endif
 
 #ifdef __OBJC__