Merge branch 'master' into merge/upstream-full

Resolve conflicts after master gained the flat-file database backend,
AI client, and other cproof-fork features:

- CHANGELOG: keep cproof-fork unreleased section atop full upstream
  history (0.17.0 / 0.16.0 / 0.15.1)
- src/command/cmd_ac.c: keep both upstream spellcheck AC and cproof
  /history switch|verify|export|import autocompletion
- src/config/preferences.c: merge upstream [spellcheck] group with the
  cproof [ai]/[ai/<provider>] groups
- src/database.c: take master (thin dispatcher); upstream SQLite
  improvements (v3 migration, auto_gchar) belong in database_sqlite.c
  and will land in a follow-up commit
- src/tools/autocomplete.c: take upstream unescape of search_str
- src/ui/statusbar.c: keep guint signatures (per project preference)
  and adapt _status_bar_draw_dbbackend to guint as well
- src/xmpp/jid.c: combine the new jid_is_valid/jid_is_valid_user_jid
  with the "(null)" legacy-placeholder guard in
  jid_create_from_bare_and_resource; use auto_gchar
- tests/functionaltests/proftest.c: keep unsigned-safe pre-check on
  output_len before subtracting OUTPUT_BUF_SIZE
- tests/unittests/unittests.c: keep upstream subdirectory include
  layout plus cproof-only test_ai_client/database_export/database_stress
- tests/unittests/test_jid.c: drop orphan top-level copy (the
  restructured version lives in tests/unittests/xmpp/test_jid.c)

Upstream is included up to 1ac05754b (release 0.18.0 era). Follow-up:
pull 1ac05754b..upstream/master (esp. 42a849d16 db migration fix and
4749645c7 receipt-request restore), and adapt the SQLite improvements
into database_sqlite.c.

src/ui/ui.h

@@ -309,7 +309,6 @@ void cons_history_setting(void);
 void cons_carbons_setting(void);
 void cons_receipts_setting(void);
 void cons_log_setting(void);
-void cons_logging_setting(void);
 void cons_autoaway_setting(void);
 void cons_reconnect_setting(void);
 void cons_autoping_setting(void);
@@ -365,6 +364,8 @@ ProfWin* win_create_config(const char* const title, DataForm* form, ProfConfWinC
 ProfWin* win_create_private(const char* const fulljid);
 ProfWin* win_create_plugin(const char* const plugin_name, const char* const tag);
 ProfWin* win_create_vcard(vCard* vcard);
+ProfWin* win_create_ai(AISession* session);
+ProfWin* wins_new_ai(AISession* session);
 void win_update_virtual(ProfWin* window);
 void win_free(ProfWin* window);
 gboolean win_notify_remind(ProfWin* window);
@@ -424,4 +425,9 @@ void notify_invite(const char* const from, const char* const room, const char* c
 void notify(const char* const message, int timeout, const char* const category);
 void notify_subscription(const char* const from);
 
+/* AI window */
+char* aiwin_get_string(ProfAiWin* win);
+void aiwin_display_response(ProfAiWin* win, const char* response);
+void aiwin_display_error(ProfAiWin* win, const char* error_msg);
+
 #endif