[core] Expose edgesForExtendedLayout for pre-iOS 7 SDK availability.
[catalog] Modernize BasicInstantiationAttributedLabelViewController.m.
[attributedlabel] Start upgrading to iOS 6 base support.
[attributedlabel] Don't obfuscate the data detection links.

For whatever reason data dection links were being replaced with generic
URL links, causing crashes for links that were in fact phone numbers or
addresses.
[attributedlabel] Modernize NSMutableAttributedString+NimbusAttributedLabel.m.
Merge branch 'attributedlabel'