Small perfomance optimization in Directives and Tag methods (#1112)

src/directives.cpp

@@ -3,7 +3,7 @@
 namespace YAML {
 Directives::Directives() : version{true, 1, 2}, tags{} {}
 
-const std::string Directives::TranslateTagHandle(
+std::string Directives::TranslateTagHandle(
     const std::string& handle) const {
   auto it = tags.find(handle);
   if (it == tags.end()) {

src/directives.h

@@ -19,7 +19,7 @@ struct Version {
 struct Directives {
   Directives();
 
-  const std::string TranslateTagHandle(const std::string& handle) const;
+  std::string TranslateTagHandle(const std::string& handle) const;
 
   Version version;
   std::map<std::string, std::string> tags;

src/tag.cpp

@@ -29,7 +29,7 @@ Tag::Tag(const Token& token)
   }
 }
 
-const std::string Tag::Translate(const Directives& directives) {
+std::string Tag::Translate(const Directives& directives) {
   switch (type) {
     case VERBATIM:
       return value;

src/tag.h

@@ -23,7 +23,7 @@ struct Tag {
   };
 
   Tag(const Token& token);
-  const std::string Translate(const Directives& directives);
+  std::string Translate(const Directives& directives);
 
   TYPE type;
   std::string handle, value;