Announce new prefdir, preferences functions and add to manual. * NEWS: Add prefdir, preferences to list of new functions for 3.8. * doc/interpreter/gui.txi: Add prefdir, preferences to manual. * scripts/help/__unimplemented__.m: Remove functions from list of unimplemented. * scripts/prefs/prefdir.m: Add @seealso references to docstring. * scripts/prefs/preferences.m: Use prefsfile() instead of creating name. * scripts/prefs/private/prefsfile.m: Use filesep() instead of '/' for Windows users.

--- a/doc/interpreter/gui.txi
+++ b/doc/interpreter/gui.txi
@@ -81,13 +81,17 @@
 @node User-Defined Preferences
 @section User-Defined Preferences
 
+@DOCSTRING(getpref)
+
+@DOCSTRING(setpref)
+
 @DOCSTRING(addpref)
 
-@DOCSTRING(getpref)
+@DOCSTRING(rmpref)
 
 @DOCSTRING(ispref)
 
-@DOCSTRING(rmpref)
+@DOCSTRING(prefdir)
 
-@DOCSTRING(setpref)
+@DOCSTRING(preferences)