Patch for oct-stream.cc

[Michael Goffioul]

MSVC complains it cannot add 2 pointers. The following patch solves
it. (Does this really compile under gcc?)

Michael.

Index: src/oct-stream.cc
===================================================================
RCS file: /cvs/octave/src/oct-stream.cc,v
retrieving revision 1.136
diff -c -r1.136 oct-stream.cc
*** src/oct-stream.cc   10 Feb 2007 07:10:42 -0000      1.136
--- src/oct-stream.cc   10 Feb 2007 08:22:14 -0000
***************
*** 2729,2735 ****
 {
   // Note that this is not ::error () !

!   error (who, "stream not open for " + rw);
 }

 octave_stream::octave_stream (octave_base_stream *bs)
--- 2726,2732 ----
 {
   // Note that this is not ::error () !

!   error (who, std::string("stream not open for ") + rw);
 }

 octave_stream::octave_stream (octave_base_stream *bs)