Replace all occurences of PLATFORMS file with reference to the ARM

The conf.py exclude_patterns now includes platforms.rst to avoid
problems with redefining labels:
https://github.com/sphinx-doc/sphinx/issues/1668#issuecomment-71376208

README.md

@@ -58,7 +58,9 @@ CHANGES file format.
 For up-to-date versions and release notes, see
 [https://www.isc.org/download/](https://www.isc.org/download/).
 
-For information about supported platforms, see [PLATFORMS](PLATFORMS.md).
+For information about supported platforms, see the
+["Supported Platforms"](doc/arm/platforms.rst) section in the BIND 9
+Administrator Reference Manual.
 
 ### <a name="help"/> Reporting bugs and getting help
 

doc/arm/Makefile.am

@@ -20,6 +20,7 @@ EXTRA_DIST =					\
 	manpages.rst				\
 	notes.rst				\
 	pkcs11.rst				\
+	platforms.rst				\
 	plugins.rst				\
 	reference.rst				\
 	requirements.rst			\

doc/arm/conf.py

@@ -150,6 +150,7 @@ exclude_patterns = [
     'logging-cattegories.rst',
     'managed-keys.rst',
     'pkcs11.rst',
+    'platforms.rst',
     'plugins.rst'
     ]
 

doc/arm/notes.rst

@@ -27,23 +27,7 @@ detailed list of changes and bug fixes.
 Supported Platforms
 -------------------
 
-To build on Unix-like systems, BIND requires support for POSIX.1c
-threads (IEEE Std 1003.1c-1995), the Advanced Sockets API for IPv6
-(:rfc:`3542`), and standard atomic operations provided by the C
-compiler.
-
-The libuv asynchronous I/O library and the OpenSSL cryptography library
-must be available for the target platform. A PKCS#11 provider can be
-used instead of OpenSSL for Public Key cryptography (i.e., DNSSEC
-signing and validation), but OpenSSL is still required for general
-cryptography operations such as hashing and random number generation.
-
-More information can be found in the ``PLATFORMS.md`` file that is
-included in the source distribution of BIND 9. If your compiler and
-system libraries provide the above features, BIND 9 should compile and
-run. If that is not the case, the BIND development team will generally
-accept patches that add support for systems that are still supported by
-their respective vendors.
+See the :ref:`supported_os` section in the :ref:`Requirements` chapter.
 
 Download
 --------

doc/arm/platforms.rst

@@ -9,6 +9,8 @@
 .. See the COPYRIGHT file distributed with this work for additional
 .. information regarding copyright ownership.
 
+.. _supported_os:
+
 Supported platforms
 -------------------
 

doc/arm/requirements.rst

@@ -9,7 +9,7 @@
 .. See the COPYRIGHT file distributed with this work for additional
 .. information regarding copyright ownership.
 
-.. Requirements:
+.. _Requirements:
 
 BIND Resource Requirements
 ==========================
@@ -70,6 +70,4 @@ much memory or CPU power as in the first alternative, but this has the
 disadvantage of making many more external queries, as none of the name
 servers share their cached data.
 
-.. _supported_os:
-
 .. include:: platforms.rst