UPGRADE: Add note for REF_DEBUG flag

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Merged revisions 414345 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 414346 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 414347 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@414348 65c4cc65-6c06-0410-ace0-fbb531ad65f3

UPGRADE.txt

@@ -35,6 +35,14 @@ From 12 to 13:
    an older version of rasterisk connects to the new version then the
    "core set verbose" command will have no effect.
 
+ - Added a new Compiler Flag, REF_DEBUG. When enabled, reference counted
+   objects will emit additional debug information to the refs log file located
+   in the standard Asterisk log file directory. This log file is useful in
+   tracking down object leaks and other reference counting issues. Prior to
+   this version, this option was only available by modifying the source code
+   directly. This change also includes a new script, refcounter.py, in the
+   contrib folder that will process the refs log file.
+
 ARI:
  - The ARI version has been changed from 1.0.0 to 1.1.0. This is to reflect
    the backwards compatible changes listed below.