[clang-tidy] use auto (#888)

Found with modernize-use-auto
Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/directives.cpp

@@ -5,7 +5,7 @@ Directives::Directives() : version{true, 1, 2}, tags{} {}
 
 const std::string Directives::TranslateTagHandle(
     const std::string& handle) const {
-  std::map<std::string, std::string>::const_iterator it = tags.find(handle);
+  auto it = tags.find(handle);
   if (it == tags.end()) {
     if (handle == "!!")
       return "tag:yaml.org,2002:";

src/node_data.cpp

@@ -110,9 +110,9 @@ void node_data::compute_seq_size() const {
 }
 
 void node_data::compute_map_size() const {
-  kv_pairs::iterator it = m_undefinedPairs.begin();
+  auto it = m_undefinedPairs.begin();
   while (it != m_undefinedPairs.end()) {
-    kv_pairs::iterator jt = std::next(it);
+    auto jt = std::next(it);
     if (it->first->is_defined() && it->second->is_defined())
       m_undefinedPairs.erase(it);
     it = jt;
@@ -248,9 +248,8 @@ bool node_data::remove(node& key, const shared_memory_holder& /* pMemory */) {
   if (m_type != NodeType::Map)
     return false;
 
-  for (kv_pairs::iterator it = m_undefinedPairs.begin();
-       it != m_undefinedPairs.end();) {
-    kv_pairs::iterator jt = std::next(it);
+  for (auto it = m_undefinedPairs.begin(); it != m_undefinedPairs.end();) {
+    auto jt = std::next(it);
     if (it->first->is(key))
       m_undefinedPairs.erase(it);
     it = jt;

src/nodeevents.cpp

@@ -13,7 +13,7 @@ void NodeEvents::AliasManager::RegisterReference(const detail::node& node) {
 
 anchor_t NodeEvents::AliasManager::LookupAnchor(
     const detail::node& node) const {
-  AnchorByIdentity::const_iterator it = m_anchorByIdentity.find(node.ref());
+  auto it = m_anchorByIdentity.find(node.ref());
   if (it == m_anchorByIdentity.end())
     return 0;
   return it->second;
@@ -92,7 +92,7 @@ void NodeEvents::Emit(const detail::node& node, EventHandler& handler,
 }
 
 bool NodeEvents::IsAliased(const detail::node& node) const {
-  RefCount::const_iterator it = m_refCount.find(node.ref());
+  auto it = m_refCount.find(node.ref());
   return it != m_refCount.end() && it->second > 1;
 }
 }  // namespace YAML

src/singledocparser.cpp

@@ -422,7 +422,7 @@ anchor_t SingleDocParser::RegisterAnchor(const std::string& name) {
 
 anchor_t SingleDocParser::LookupAnchor(const Mark& mark,
                                        const std::string& name) const {
-  Anchors::const_iterator it = m_anchors.find(name);
+  auto it = m_anchors.find(name);
   if (it == m_anchors.end())
     throw ParserException(mark, ErrorMsg::UNKNOWN_ANCHOR);