Load structures with arbitrary string fieldnames (bug #50831, bug #46645). * ls-oct-text.h, ls-oct-text.cc (read_text_data): Consider additional optional bool argument to skip validation of input name. * ov-struct.cc (octave_struct::load_ascii, octave_scalar_struct::load_ascii): Call read_text_data with additional argument (skip_validation), set to true. * test/bug-50831/bug-50831.tst, test/bug-50831/module.mk: New test files.

%!function out = bug54490 ()
%!  global k;
%!  k = 1;
%!  out = 3;
%!endfunction

%!test
%! global k;
%! k = 2;
%! a = [5, 6];
%! a(k) = bug54490 ();
%! assert (a, [5, 3]);
%! k = 2;
%! a = [5, 6];
%! [a(k)] = bug54490 ();
%! assert (a, [5, 3]);
%! clear -global k;  # cleanup after test