Add subsystem for managing information for classdef objects in MAT-files (bug #45833).

* libinterp/corefcn/ls-mat-subsys.h: Add new class octave::subsystem_handler to
manage subsystem data.
* libinterp/corefcn/ls-mat-subsys.cc: Add new file containing methods to read
and write subsystem data in MAT-files.
* libinterp/corefcn/module.mk: Include new files in build system.

* libinterp/corefcn/load-save.h (load_save_system): Add new member
m_subsystem_handler to manage subsystem_handler object.
* libinterp/corefcn/load-save.cc (load_save_system::create_subsystem_handler,
load_save_system::get_subsystem_handler,
load_save_system::clear_subsystem_handler): Add new methods to access and
manage m_subsystem_handler.

Author: Nithin Lakshmisha

libinterp/corefcn/load-save.cc

@@ -78,6 +78,7 @@
 #include "ls-mat5.h"
 #include "ls-oct-text.h"
 #include "ls-oct-binary.h"
+#include "ls-mat-subsys.h"
 
 // Remove gnulib definitions, if any.
 #if defined (close)
@@ -1622,6 +1623,24 @@ load_save_system::get_mcos_object_cache_id (const void *obj, bool& new_entry)
   return id;
 }
 
+void
+load_save_system::create_subsystem_handler ()
+{
+  m_subsystem_handler = std::make_unique<subsystem_handler> ();
+}
+
+subsystem_handler*
+load_save_system::get_subsystem_handler ()
+{
+  return m_subsystem_handler.get ();
+}
+
+void
+load_save_system::clear_subsystem_handler ()
+{
+  m_subsystem_handler.reset ();
+}
+
 DEFMETHOD (load, interp, args, nargout,
            doc: /* -*- texinfo -*-
 @deftypefn  {} {} load file

libinterp/corefcn/load-save.h

@@ -41,6 +41,7 @@ OCTAVE_BEGIN_NAMESPACE(octave)
 class interpreter;
 class load_save_format;
 class symbol_info;
+class subsystem_handler;
 
 class load_save_system
 {
@@ -208,8 +209,17 @@ class load_save_system
   OCTINTERP_API uint32_t
   get_mcos_object_cache_id (const void *obj, bool& new_entry);
 
+  OCTINTERP_API void create_subsystem_handler ();
+
+  OCTINTERP_API subsystem_handler * get_subsystem_handler ();
+
+  OCTINTERP_API void clear_subsystem_handler ();
+
 private:
 
+  // Subsystem handler is used to read and write MCOS objects in MAT-files
+  std::unique_ptr<subsystem_handler> m_subsystem_handler;
+
   interpreter& m_interpreter;
 
   // Write octave-workspace file if Octave crashes or is killed by a