Always process target events in the main UI

This makes target events always be always processed with the main UI
as current UI.  This way, warnings, debug output, etc. are always
consistently sent to the main console.

gdb/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* event-top.c (restore_ui_cleanup): Make extern.
	* infrun.c (fetch_inferior_event): Always switch to the main UI.
	* top.h (restore_ui_cleanup): Declare.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2016-06-21  Pedro Alves  <palves@redhat.com>
+
+	* event-top.c (restore_ui_cleanup): Make extern.
+	* infrun.c (fetch_inferior_event): Always switch to the main UI.
+	* top.h (restore_ui_cleanup): Declare.
+
 2016-06-21  Pedro Alves  <palves@redhat.com>
 
 	PR mi/20034

gdb/event-top.c

@@ -456,9 +456,9 @@ struct ui *main_ui = &main_ui_;
 struct ui *current_ui = &main_ui_;
 struct ui *ui_list = &main_ui_;
 
-/* Cleanup that restores the current UI.  */
+/* See top.h.  */
 
-static void
+void
 restore_ui_cleanup (void *data)
 {
   current_ui = (struct ui *) data;

gdb/infrun.c

@@ -3879,6 +3879,12 @@ fetch_inferior_event (void *client_data)
 
   memset (ecs, 0, sizeof (*ecs));
 
+  /* Events are always processed with the main UI as current UI.  This
+     way, warnings, debug output, etc. are always consistently sent to
+     the main console.  */
+  make_cleanup (restore_ui_cleanup, current_ui);
+  current_ui = main_ui;
+
   /* End up with readline processing input, if necessary.  */
   make_cleanup (reinstall_readline_callback_handler_cleanup, NULL);
 

gdb/top.h

@@ -141,6 +141,9 @@ extern void switch_thru_all_uis_next (struct switch_thru_all_uis *state);
        switch_thru_all_uis_cond (&STATE);		\
        switch_thru_all_uis_next (&STATE))
 
+/* Cleanup that restores the current UI.  */
+extern void restore_ui_cleanup (void *data);
+
 /* From top.c.  */
 extern char *saved_command_line;
 extern int in_user_command;