These data formatters make the string value appear in Xcode's variables view (and on the command line) without having to expand the data structure.
I don't think you need to go back and cover all the ones already added, but could we start adding tests for new lldb/llvm data formatters as we add them? That way we can keep them useful as people change llvm.
It's not quite obvious to me how to write a test for this. The test would need to live in LLDB, and it would need to compile a program linking against a variant of libSupport that was compiled with debug info. I'm not sure how to best do this.