cmOutputConverter: Adopt EscapeWindowsShellArgument method

Move it out of cmSystemTools and into cmOutputConverter.

Source/cmSystemTools.h

@@ -256,11 +256,6 @@ public:
   static void ParseUnixCommandLine(const char* command,
                                    std::vector<std::string>& args);
 
-  /** Compute an escaped version of the given argument for use in a
-      windows shell.  See kwsys/System.h.in for details.  */
-  static std::string EscapeWindowsShellArgument(const char* arg,
-                                                int shell_flags);
-
   static void EnableMessages() { s_DisableMessages = false; }
   static void DisableMessages() { s_DisableMessages = true; }
   static void DisableRunCommandOutput() {s_DisableRunCommandOutput = true; }