Add a bool->StringRef c'tor to StringRef.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187166 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/StringRef.h

@@ -90,6 +90,10 @@ namespace llvm {
     /*implicit*/ StringRef(const std::string &Str)
       : Data(Str.data()), Length(Str.length()) {}
 
+    /// Construct a string ref from a boolean.
+    explicit StringRef(bool B)
+      : Data(B ? "true" : "false"), Length(::strlen(Data)) {}
+
     /// @}
     /// @name Iterators
     /// @{