isdir.m: Make m-file a legacy function (bug #54489) * isdir.m: Note that function is not recommended in docstring. Add 1-time warning about function being obsolete. Add first time BIST test to provoke and suppress warning. * scripts/legacy/module.mk, scripts/miscellaneous/module.mk: Move isdir.m from miscellaneous/ dir to legacy/ dir. * NEWS: Announce change to legacy function. * syscalls.cc (Fstat): Add isfolder to @seealso link. * utils.cc (Fis_absolute_filename, Fis_rooted_relative_filename, Fmake_absolute_filename): Replace isdir with isfolder in @seealso links. * uigetdir.m, uigetfile.m, uiputfile.m, which.m, copyfile.m, mkdir.m, movefile.m, tempdir.m, unpack.m, what.m, __print_parse_opts__.m, compare_plot_demos.m, rundemos.m, runtests.m: Replace instances of isdir with isfolder in core Octave.

--- a/scripts/gui/uigetdir.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/gui/uigetdir.m	Mon Aug 13 12:17:58 2018 -0700
@@ -40,7 +40,7 @@
     error ("uigetdir: INIT_PATH and DIALOG_NAME must be string arguments");
   endif
 
-  if (! isdir (init_path))
+  if (! isfolder (init_path))
     init_path = fileparts (init_path);
   endif