improve handling of global symbols (bug #53599) * load-save.cc (install_loaded_variable): For global values, check global status and link to global symbol if needed. * symrec.h (symbol_record::symbol_record_rep::unbind_global_rep): New function. (symbol_record::symbol_record_rep::clear): Use unbind_global_rep to clearing global symbols. (symbol_record::symbol_record_rep::is_marked_global): New function. (symbol_record::symbol_record_rep::is_global): Use it. (symbol_record::symbol_record_rep::bind_fwd_rep): Don't forward again if symbol is already global. (symbol_record::unbind_fwd_rep): Eliminate argument. Change all uses. (symbol_record::symbol_record_rep::unbind_fwd_rep): Eliminate argument. Simplify. * test/bug-53599.tst: New file. * test/module.mk: Update.

%!function rval = sggval (val)
%!  global gval
%!  if (nargin == 1)
%!    gval = val;
%!  else
%!    rval = gval;
%!  endif
%!endfunction

%!test
%! global gval
%! assert (isempty (gval))
%! sggval (13);
%! assert (sggval (), 13);
%! assert (gval, 13);
%! clear global gval
%! assert (sggval (), [])
%! gval = 42;
%! assert (sggval (), []);
%! clear gval
%! global gval
%! gval = 42;
%! assert (sggval (), 42);