Update CHANGES and UPGRADE.txt for 18.0.0

CHANGES

@@ -12,6 +12,28 @@
 ===
 ==============================================================================
 
+------------------------------------------------------------------------------
+--- Functionality changes from Asterisk 17.0.0 to Asterisk 18.0.0 ------------
+------------------------------------------------------------------------------
+
+chan_pjsip
+------------------
+ * The PJSIP_SEND_SESSION_REFRESH dialplan function now issues a warning, and
+   returns unsuccessful if it's used on a channel prior to answering.
+
+logger
+------------------
+ * Added a new log formatter called "plain" that always prints
+   file, function and line number if available (even for verbose
+   messages) and never prints color control characters.  Most
+   suitable for file output but can be used for other channels
+   as well.
+
+   You use it in logger.conf like so:
+   debug => [plain]debug
+   console => [plain]error,warning,debug,notice,pjsip_history
+   messages => [plain]warning,error,verbose
+
 ------------------------------------------------------------------------------
 --- New functionality introduced in Asterisk 18.0.0 --------------------------
 ------------------------------------------------------------------------------

doc/CHANGES-staging/logger_format.txt

-Subject: logger
-
-Added a new log formatter called "plain" that always prints
-file, function and line number if available (even for verbose
-messages) and never prints color control characters.  Most
-suitable for file output but can be used for other channels
-as well.
-
-You use it in logger.conf like so:
-debug => [plain]debug
-console => [plain]error,warning,debug,notice,pjsip_history
-messages => [plain]warning,error,verbose

doc/CHANGES-staging/pjsip_send_session_refresh.txt

-Subject: chan_pjsip
-
-The PJSIP_SEND_SESSION_REFRESH dialplan function now issues a warning, and
-returns unsuccessful if it's used on a channel prior to answering.