allow help to find docstrings for classdef classes and methods (bug #43047) * help.cc (help_system::raw_help_from_symbol_table): Also find docstrings from classdef meta objects (both classes and methods). * cdef-class.h, cdef-class.cc (cdef_class::cdef_class_rep, cdef_class): Store docstring for class and provide access. * ov-classdef.h, ov-classdef.cc (octave_classdef_meta::doc_string): New function to provide access to doc strings for classdef objects and methods. * ov-fcn.h (octave_function::doc_string): Now virtual. New argument for method name.

--- a/libinterp/octave-value/ov-fcn.h	Fri May 29 10:56:22 2020 -0400
+++ b/libinterp/octave-value/ov-fcn.h	Fri May 29 10:57:04 2020 -0400
@@ -223,7 +223,11 @@
 
   void document (const std::string& ds) { doc = ds; }
 
-  std::string doc_string (void) const { return doc; }
+  virtual std::string
+  doc_string (const std::string& /*meth_name*/ = "") const
+  {
+    return doc;
+  }
 
   virtual void unload (void) { }