COMP: Added istringstream::clear() method to disambiguate the call from using string::clear or istrstream::clear.

Source/kwsys/kwsys_ios_sstream.h.in

@@ -173,6 +173,10 @@ public:
     this->~istringstream();
     new (this) istringstream(s);
     }
+  void clear(int flags)
+    {
+    this->IStrStream::clear(flags);
+    }
 private:
   istringstream(const istringstream&);
   void operator=(const istringstream&);