Update usage comments in Printable.h. NFC.

[frasercrmck]

Summary

The example wouldn't compile, and used an invalid case style for a
function.

[MatzeB]

LGTM

llvm/include/llvm/Support/Printable.h

 namespace llvm {
 
 class raw_ostream;
 
 /// Simple wrapper around std::function<void(raw_ostream&)>.
 /// This class is useful to construct print helpers for raw_ostream.
 ///
 /// Example:
-///     Printable PrintRegister(unsigned Register) {
+///     Printable printRegister(unsigned Register) {
 ///       return Printable([Register](raw_ostream &OS) {
 ///         OS << getRegisterName(Register);
-///       }
-///     }
-///     ... OS << PrintRegister(Register); ...
+///       });
+///     }
+///     ... OS << printRegister(Register); ...
 ///
 /// Implementation note: Ideally this would just be a typedef, but doing so
 /// leads to operator << being ambiguous as function has matching constructors
 /// in some STL versions. I have seen the problem on gcc 4.6 libstdc++ and
 /// microsoft STL.
 class Printable {
 public:
   std::function<void(raw_ostream &OS)> Print;
   Printable(std::function<void(raw_ostream &OS)> Print)
       : Print(std::move(Print)) {}
 };
 
 inline raw_ostream &operator<<(raw_ostream &OS, const Printable &P) {
   P.Print(OS);
   return OS;
 }
 
-}
+} // namespace llvm
 
 #endif