Merged revisions 216080 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.2

........
  r216080 | russell | 2009-09-03 14:35:23 -0500 (Thu, 03 Sep 2009) | 2 lines
  
  Add a note about IAX2 to UPGRADE.txt.
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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@216085 65c4cc65-6c06-0410-ace0-fbb531ad65f3

UPGRADE.txt

@@ -6,6 +6,14 @@
 === UPGRADE.txt     -- Upgrade info for 1.2 to 1.4
 =========================================================
 
+IAX2:
+
+* There have been some changes to the IAX2 protocol to address the security
+  concerns documented in the security advisory AST-2009-006.  Please see the
+  IAX2 security document, doc/IAX2-security.pdf, for information regarding
+  backwards compatibility with versions of Asterisk that do not contain these
+  changes to IAX2.
+
 Build Process (configure script):
 
 Asterisk now uses an autoconf-generated configuration script to learn how it