If you like to show a status bar under iOS 7 with Xcode 5, just rearrange the buttons and other subviews to make enough space around the status bar. But, just wait! I like to support iOS 6 too. How do I do that?
I found documentation from Apple, and found the "Supporting Two Versions of a Standard App" title in the document.
If you are editing an XIB file, select it and click assistant editor. You will able to find the "manual, automatic..." menu around there. Then choose "preview".

Then you'll find a view layout side by side. Then you will notice that there is a popup button around the right bottom of the right pane (view); it says "iOS 7 and later". You can choose "iOS 6.1 and earlier". Woa! Now you can make adjustments for iOS 6.1 without affecting the layout of iOS 7.

If you are working on the storyboard, it is basically the same. You choose a view controller object, and click assistant editor mode, choose "preview", then "iOS7 and later"... Bluh Bluh Bluh.
I'm not sure, but only the assistant editor is capable of switching to iOS 7+/iOS 6- mode. I just found this very recently, so please point out, if there are any misunderstandings or other tricks.