iOS 13 adaptation

[dengfeng520]

1、Fix the problem of demo build failed on Xcode 11.
2、Fix the iOS 13 system, after presentViewController, the bottom of the Cancel and confirmBtn buttons do not display the issues.
I use NSLayoutConstraint , I think this is compatible with some phones before iPhone X.

   cancelBtn.translatesAutoresizingMaskIntoConstraints = false;
    [[cancelBtn.leftAnchor constraintEqualToAnchor:self.view.leftAnchor constant:0] setActive:true];
    if (@available(iOS 11.0, *)) {
        [[cancelBtn.bottomAnchor constraintEqualToAnchor:self.view.safeAreaLayoutGuide.bottomAnchor constant:0] setActive:true];
    } else {
        [[cancelBtn.bottomAnchor constraintEqualToAnchor:self.view.bottomAnchor constant:0] setActive:true];
    }
    [[cancelBtn.widthAnchor constraintEqualToConstant:100] setActive:true];
    [[cancelBtn.heightAnchor constraintEqualToConstant:50] setActive:true];