Add vCard support

Only nicknames, photos, birthdays, addresses, telephone numbers, emails,
JIDs, titles, roles, notes, and URLs are supported

Due to the synopsis array not having enough space, `/vcard photo
open-self` and `/vcard photo save-self` are not documented properly in
the synopsis section of the `/vcard` command, but they are documented in
the arguments section

Fixed memory leak in vcard autocomplete (thanks to debXwoody)

tests/unittests/ui/stub_ui.c

@@ -1256,6 +1256,11 @@ win_create_plugin(const char* const plugin_name, const char* const tag)
 {
     return NULL;
 }
+ProfWin*
+win_create_vcard(vCard* vcard)
+{
+    return NULL;
+}
 
 char*
 win_get_tab_identifier(ProfWin* window)

tests/unittests/ui/stub_vcardwin.c

@@ -0,0 +1,4 @@
+void
+vcardwin_update(void)
+{
+}