Revert "Fix compile warning with -Wshadow"

This reverts commit 1f5e971f77.

See #1306; the previous commit caused an error with -Wpedantic:

yaml-cpp/include/yaml-cpp/emitterstyle.h:13:2: error: extra ‘;’ [-Wpedantic]

Since the original commit was to resolve warnings, reverting and the OP can produce a new one that fixes this issue.

include/yaml-cpp/emitterstyle.h

@@ -8,8 +8,8 @@
 #endif
 
 namespace YAML {
-namespace EmitterStyle {
-enum value { Default, Block, Flow };
+struct EmitterStyle {
+  enum value { Default, Block, Flow };
 };
 }
 

include/yaml-cpp/node/type.h

@@ -8,8 +8,8 @@
 #endif
 
 namespace YAML {
-namespace NodeType {
-enum value { Undefined, Null, Scalar, Sequence, Map };
+struct NodeType {
+  enum value { Undefined, Null, Scalar, Sequence, Map };
 };
 }
 

src/singledocparser.cpp

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include <cstdio>
 #include <sstream>
 
@@ -92,8 +93,8 @@ void SingleDocParser::HandleNode(EventHandler& eventHandler) {
   // add non-specific tags
   if (tag.empty())
     tag = (token.type == Token::NON_PLAIN_SCALAR ? "!" : "?");
-
-  if (token.type == Token::PLAIN_SCALAR
+  
+  if (token.type == Token::PLAIN_SCALAR 
       && tag.compare("?") == 0 && IsNullString(token.value)) {
     eventHandler.OnNull(mark, anchor);
     m_scanner.pop();