Facebook iOS SDK 3.12

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

Upgrading:
    https://developers.facebook.com/docs/ios/upgrading/
Merge github.com:facebook/facebook-ios-sdk (v3.12)

Conflicts:
	src/Legacy/FBDialog.m
	src/UI/FBFriendPickerViewController.m
	src/facebook-ios-sdk.xcodeproj/project.pbxproj