patch 9.1.0265: console dialog cannot save unnamed buffers

Problem:  console dialog cannot save unnamed buffers
Solution: set bufname before save (glepnir). Define dialog_con_gui
          to test for GUI+Console dialog support, use it to skip
          the test when the GUI feature has been defined.

Note: The dialog_changed() function will also try to call the
browse_save_fname() function, when FEAT_BROWSE is defined (which is only
defined in a GUI build of Vim). This will eventually lead to a call of
do_browse(), which causes an error message if a GUI is not currently
running (see the TODO: in do_browse()) and will then lead to a failure
in Test_goto_buf_with_onfirm().

Therefore, we must disable the Test_goto_buf_with_onfirm(), when the
dialog_con_gui feature is enabled (which basically means dialog feature
for GUI and Console builds, in contrast to the dialog_con and dialog_gui
feature).

(Previously this wasn't a problem, because the test aborted in the YES
case for the :confirm :b XgotoConf case and did therefore not run into
the browse function call)

closes: #14398

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 6a4c8d9..fb7c794 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2024 Apr 03
+*builtin.txt*	For Vim version 9.1.  Last change: 2024 Apr 04
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1771,7 +1771,7 @@
 		made.  It returns the number of the choice.  For the first
 		choice this is 1.
 		Note: confirm() is only supported when compiled with dialog
-		support, see |+dialog_con| and |+dialog_gui|.
+		support, see |+dialog_con| |+dialog_con_gui| and |+dialog_gui|.
 
 		{msg} is displayed in a |dialog| with {choices} as the
 		alternatives.  When {choices} is missing or empty, "&OK" is
@@ -11200,6 +11200,7 @@
 cursorbind		Compiled with |'cursorbind'| (always true)
 debug			Compiled with "DEBUG" defined.
 dialog_con		Compiled with console dialog support.
+dialog_con_gui		Compiled with console and GUI dialog support.
 dialog_gui		Compiled with GUI dialog support.
 diff			Compiled with |vimdiff| and 'diff' support.
 digraphs		Compiled with support for digraphs.