upgrade: Add 2.4.1

Author: sirainen

docs/installation/upgrade/2.4-to-2.4.x.md

@@ -0,0 +1,27 @@
+---
+layout: doc
+title: 2.4 to 2.4.x
+dovecotlinks:
+  upgrading-2.4-to-2.4: Upgrading Dovecot CE from 2.4 to 2.4.x
+---
+
+# Upgrading Dovecot CE from 2.4 to 2.4.x
+
+## Dovecot CE
+
+### v2.4.0 to v2.4.1
+
+ * Added `MALLOC_MMAP_THRESHOLD_=131072` to [[setting,import_environment]] when
+   building with glibc. Note that [[setting,dovecot_config_version]] value does
+   not affect change - it's always added.
+
+#### Changed Setting Defaults
+
+These changes don't take effect until [[setting,dovecot_config_version]] is
+changed from `2.4.0` to `2.4.1`.
+
+| Setting | Old Default Value | New Default Value |
+| ------- | ----------------- | ----------------- |
+| [[setting,mail_cache_fields]] | flags | flags hdr.date hdr.subject hdr.from hdr.sender hdr.reply-to hdr.to hdr.cc hdr.bcc hdr.in-reply-to hdr.message-id date.received size.virtual imap.bodystructure mime.parts hdr.references hdr.importance hdr.x-priority hdr.x-open-xchange-share-url pop3.uidl pop3.order |
+| `service/auth/unix_listener/auth-userdb/group` | (empty = root) | `$SET:default_internal_group` |
+| `service/lmtp/restart_request_count` | unlimited | 1 |