Fix memory leak in iOS 5 and 6

...when calling "- [NSCachedURLResponse data]"

It gets the data in an @autoreleasepool, gets the retain count and check it again outside the @autorelease pool.
If the count is the same (it should have gone down by one), memory was leaked and we manually release it.

The "#ifndef __clang_analyzer__" is there so the static analyser doesn't report it as code releasing something it doesn't own (which is what we do since the owner forgot to do it).