Facebook iOS SDK 3.13

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
Facebook iOS SDK 3.13.1

Summary:
    see https://developers.facebook.com/ios/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
- Fixed Xcode 6 build errors
Merge branch 'build_fix' into sdk-version-3.12.0-fixed

Conflicts:
	src/FBSessionLoginStrategy.h