cmXMLParser: Remove unused IsSpace method

Source/cmXMLParser.cxx

@@ -2,7 +2,6 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmXMLParser.h"
 
-#include <cctype>
 #include <cstring>
 #include <iostream>
 #include <sstream>
@@ -143,11 +142,6 @@ void cmXMLParser::CharacterDataHandler(const char* /*inData*/,
 {
 }
 
-int cmXMLParser::IsSpace(char c)
-{
-  return isspace(c);
-}
-
 const char* cmXMLParser::FindAttribute(const char** atts,
                                        const char* attribute)
 {

Source/cmXMLParser.h

@@ -89,10 +89,6 @@ protected:
   /** Called by ReportXmlParseError with basic error info.  */
   virtual void ReportError(int line, int column, const char* msg);
 
-  //! Utility for convenience of subclasses.  Wraps isspace C library
-  // routine.
-  static int IsSpace(char c);
-
   //! Send the given buffer to the XML parser.
   virtual int ParseBuffer(const char* buffer, std::string::size_type length);