fix failure with function handles caused by changeset ea6997657614 * ov-fcn-handle.cc (octave_fcn_handle::set_fcn): Undo previous change. * ov-fcn.h (octave_function::src_file_name): New virtual function. * ov-builtin.h (octave_builtin::src_file_name): Rename from octave_builtin::fcn_file_name. * help.cc (do_which): Return source file name for built-in functions.

--- a/src/ov-fcn.h
+++ b/src/ov-fcn.h
@@ -61,6 +61,8 @@
 
   virtual std::string fcn_file_name (void) const { return std::string (); }
 
+  virtual std::string src_file_name (void) const { return std::string (); }
+
   // The name to show in the profiler (also used as map-key).
   virtual std::string profiler_name (void) const { return name (); }