ENH: ITstream single token append method

- remove/fully deprecated newElmt in next release

src/OpenFOAM/db/IOstreams/Tstreams/ITstream.C

@@ -402,6 +402,26 @@ void Foam::ITstream::seek(label pos)
 }
 
 
+void Foam::ITstream::append(const token& t, const bool lazy)
+{
+    reserveCapacity(tokenIndex_ + 1, lazy);
+    tokenList& toks = *this;
+
+    toks[tokenIndex_] = t;  // copy append
+    ++tokenIndex_;
+}
+
+
+void Foam::ITstream::append(token&& t, const bool lazy)
+{
+    reserveCapacity(tokenIndex_ + 1, lazy);
+    tokenList& toks = *this;
+
+    toks[tokenIndex_] = std::move(t);  // move append
+    ++tokenIndex_;
+}
+
+
 void Foam::ITstream::append(const tokenList& newTokens, const bool lazy)
 {
     reserveCapacity(tokenIndex_ + newTokens.size(), lazy);

src/OpenFOAM/db/IOstreams/Tstreams/ITstream.H

@@ -297,6 +297,14 @@ public:
 
         // Edit
 
+            //- Copy append a token at the current tokenIndex,
+            //- incrementing the index.
+            void append(const token& t, const bool lazy);
+
+            //- Move append a token at the current tokenIndex,
+            //- incrementing the index.
+            void append(token&& t, const bool lazy);
+
             //- Copy append a tokenList at the current tokenIndex,
             //- incrementing the index.
             //