stringapi: Use strings for generated file stream names

Source/cmGeneratedFileStream.cxx

@@ -249,12 +249,7 @@ int cmGeneratedFileStreamBase::RenameFile(const char* oldname,
 }
 
 //----------------------------------------------------------------------------
-void cmGeneratedFileStream::SetName(const char* fname)
+void cmGeneratedFileStream::SetName(const std::string& fname)
 {
-  if ( !fname )
-    {
-    this->Name = "";
-    return;
-    }
   this->Name = fname;
 }

Source/cmGeneratedFileStream.h

@@ -140,7 +140,7 @@ public:
    * Set name of the file that will hold the actual output. This method allows
    * the output file to be changed during the use of cmGeneratedFileStream.
    */
-  void SetName(const char* fname);
+  void SetName(const std::string& fname);
 
 private:
   cmGeneratedFileStream(cmGeneratedFileStream const&); // not implemented