Fix #2727: improve setTokenFactory in Cpp target

Change the setTokenFactory template function in the Lexer, Parser, and
TokenSource classes to be parameterized by Factory type rather than by
token type. Change the setTokenFactory signature to require the
function argument to be a Ref of the Factory template parameter type
so it can be correctly converted and assigned to the token factory
member. The type of that member is Ref<TokenFactory<CommonToken>>,
which implies that the Factory template parameter must be of a type
convertible to TokenFactory<CommonToken>.

Author: vinoski

runtime/Cpp/runtime/src/Lexer.h

@@ -95,9 +95,9 @@ namespace antlr4 {
     virtual void pushMode(size_t m);
     virtual size_t popMode();
 
-    template<typename T1>
-    void setTokenFactory(TokenFactory<T1> *factory)  {
-      this->_factory = factory;
+    template<typename Factory>
+    void setTokenFactory(Ref<Factory> const& factory)  {
+      this->_factory = std::static_pointer_cast<TokenFactory<CommonToken>>(factory);
     }
 
     virtual Ref<TokenFactory<CommonToken>> getTokenFactory() override;

runtime/Cpp/runtime/src/Parser.h

@@ -197,8 +197,8 @@ namespace antlr4 {
 
     /// <summary>
     /// Tell our token source and error strategy about a new way to create tokens. </summary>
-    template<typename T1>
-    void setTokenFactory(TokenFactory<T1> *factory)  {
+    template<typename Factory>
+    void setTokenFactory(Ref<Factory> const& factory)  {
       _input->getTokenSource()->setTokenFactory(factory);
     }
 

runtime/Cpp/runtime/src/TokenSource.h

@@ -71,8 +71,8 @@ namespace antlr4 {
     /// <seealso cref="Token"/> objects from the input.
     /// </summary>
     /// <param name="factory"> The <seealso cref="TokenFactory"/> to use for creating tokens. </param>
-    template<typename T1>
-    void setTokenFactory(TokenFactory<T1> * /*factory*/) {}
+    template<typename Factory>
+    void setTokenFactory(Ref<Factory> const& /*factory*/) {}
 
     /// <summary>
     /// Gets the <seealso cref="TokenFactory"/> this token source is currently using for