Fixed bugs when delegates add/cancel requests from delegate callbacks

Fixed bugs where callbacks via delegates or blocks could cause a crash since these might modify the downloaders, downloadInfo or downloadDelegates arrays if adding a new download request or canceling one from these.

https://github.com/rs/SDWebImage/pull/139
format the code to the right indentation.
Fix code format
Fix 64bit string formatting warnings
Fix 64bit precision loss warnings
Fix crashes on 64bit devices by casting objc_msgSend calls
Merge pull request #542 from aburgel/2.0-64bit

Fix various 64bit issues on 2.0-compat branch