Add NaCl SDK release note about LLVM 3.6 and debug metadata changes.

native_client_sdk/src/doc/devguide/devcycle/debugging.rst

 .. _devcycle-debugging:
 
 #########
 Debugging
 #########
 
 This document describes tools and techniques you can use to debug, monitor,
 and measure your application's performance.
 
 .. contents:: Table Of Contents
@@ skipping 213 matching lines @@
 <running_nacl_gdb>`
 
 Whether you publish the NMF file containing the debug URL to the
 release web server, is up to you. One reason to avoid publishing the
 debug URL is that it is only guaranteed to work for the Chrome version
 that matches the SDK version. Developers who may have left the
 ``--enable-nacl-debug`` flag turned on may end up loading the debug
 copy of your application (which may or may not work, depending on
 their version of Chrome).
 
+.. _debugging_pexes_via_nexes:
 
 Debugging PNaCl pexes (with older Pepper toolchains)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 If you want to use GDB to debug a program that is compiled with the PNaCl
 toolchain, you must convert the ``pexe`` file to a ``nexe``.  (You can skip
 this step if you are using the GCC toolchain, or if you are using
 pepper 35 or later.)
 
 * Firstly, make sure you are passing the ``-g`` :ref:`compile option
@@ skipping 295 matching lines @@
 plugin, you need to port it to Native Client (i.e., build the module with one of
 the toolchains in the NaCl SDK so that the module runs in Native Client).  For
 details on this advanced development technique, see `Debugging a Trusted Plugin
 <http://www.chromium.org/nativeclient/how-tos/debugging-documentation/debugging-a-trusted-plugin>`_.
 Note that starting with the ``pepper_22`` bundle, the NaCl SDK for Windows
 includes pre-built libraries and library source code, making it much easier to
 build a module into a .DLL.
 
 .. |menu-icon| image:: /images/menu-icon.png
 .. |puzzle| image:: /images/puzzle.png