doc: Add undocumented functions to manual for 3.6.0 release * gui.txi: New manual chapter for GUI-related functions * Makefile.am: Add new gui.txi to build * aspell-octave.en.pws: Add new words to spellcheck dictionary * io.txi: Move file I/O dialogs to gui.txi * octave.texi: Add new GUI chapter to manual * strings.txi: Add is_dq_string and is_sq_string to manual * system.txi: Add usejava to manual * guidata.m: Fix incorrect use of @deftypefn * uicontrol.m: Fix incorrect use of @deftypefn * uiresume.m: Fix incorrect use of @deftypefn * uiwait.m: Fix incorrect use of @deftypefn * addpref.m, getpref.m, ispref.m, rmpref.m, setpref.m: Adjust seealso links

--- a/scripts/plot/guidata.m
+++ b/scripts/plot/guidata.m
@@ -18,7 +18,7 @@
 
 ## -*- texinfo -*-
 ## @deftypefn  {Function File} {@var{data} =} guidata (@var{handle})
-## @deftypefnx {Function File} guidata (@var{handle}, @var{data})
+## @deftypefnx {Function File} {} guidata (@var{handle}, @var{data})
 ## @end deftypefn
 
 ## Author: goffioul