Add option to notify about version request

Cannot be configured for now.
Can be set via `adv.notify.discoversion` in the `notification` section.

Will notify about version requests via XEP-0092 and XEP-0232.

Client version can still be seen via caps (capabilities).
See `stanza_attach_caps()`.

src/config/preferences.c

@@ -1740,6 +1740,7 @@ _get_group(preference_t pref)
         case PREF_NOTIFY_MENTION_WHOLE_WORD:
         case PREF_TRAY:
         case PREF_TRAY_READ:
+        case PREF_ADV_NOTIFY_DISCO_OR_VERSION:
             return PREF_GROUP_NOTIFICATIONS;
         case PREF_CHLOG:
         case PREF_GRLOG:
@@ -1804,6 +1805,8 @@ _get_key(preference_t pref)
             return "tray";
         case PREF_TRAY_READ:
             return "tray.read";
+        case PREF_ADV_NOTIFY_DISCO_OR_VERSION:
+            return "adv.notify.discoversion";
         case PREF_INTYPE:
             return "intype";
         case PREF_HISTORY:

src/config/preferences.h

@@ -57,6 +57,7 @@ typedef enum {
     PREF_FLASH,
     PREF_TRAY,
     PREF_TRAY_READ,
+    PREF_ADV_NOTIFY_DISCO_OR_VERSION,
     PREF_INTYPE,
     PREF_HISTORY,
     PREF_CARBONS,