[#3242] Added bare-bones perfmon hook library

New files:
    arm/hooks-perfmon.rst
	src/hooks/dhcp/perfmon/.gitattributes
	src/hooks/dhcp/perfmon/.gitignore
	src/hooks/dhcp/perfmon/Makefile.am
	src/hooks/dhcp/perfmon/libloadtests/.gitignore
	src/hooks/dhcp/perfmon/libloadtests/Makefile.am
	src/hooks/dhcp/perfmon/libloadtests/load_unload_unittests.cc
	src/hooks/dhcp/perfmon/libloadtests/run_unittests.cc
	src/hooks/dhcp/perfmon/perfmon.dox
	src/hooks/dhcp/perfmon/perfmon_callouts.cc
	src/hooks/dhcp/perfmon/perfmon_log.cc
	src/hooks/dhcp/perfmon/perfmon_log.h
	src/hooks/dhcp/perfmon/perfmon_messages.cc
	src/hooks/dhcp/perfmon/perfmon_messages.h
	src/hooks/dhcp/perfmon/perfmon_messages.mes
	src/hooks/dhcp/perfmon/tests/.gitignore
	src/hooks/dhcp/perfmon/tests/Makefile.am
	src/hooks/dhcp/perfmon/tests/run_unittests.cc
	src/hooks/dhcp/perfmon/version.cc

Modified:
	configure.ac
	arm/hooks-perfmon.rst
	arm/hooks.rst
	arm/logging.rst
	arm/rst_arm_sources.mk
	conf.py
	src/hooks/dhcp/Makefile.am

doc/sphinx/arm/hooks-perfmon.rst

@@ -0,0 +1,39 @@
+.. ischooklib:: libdhcp_perfmon.so
+.. _hooks-perfmon:
+
+``libdhcp_perfmon.so``: PerfMon
+===============================
+
+This hook library can be loaded by either kea-dhcp4 or kea-dhcp6 servers
+to extend them with the ability to track and report performance related data.
+
+.. note::
+
+    This library is currently under development and not yet functional.
+
+Overview
+~~~~~~~~
+
+The library, added in Kea 2.5.6, can be loaded by the :iscman:`kea-dhcp4` or
+:iscman:`kea-dhcp6` daemon by adding it to the ``hooks-libraries`` element of
+the server's configuration:
+
+.. code-block:: javascript
+
+    {
+        "hooks-libraries": [
+            {
+                "library": "/usr/local/lib/libdhcp_perfmon.so",
+                "parameters": {
+                    ...
+                }
+            },
+            ...
+        ],
+        ...
+    }
+
+Configuration
+~~~~~~~~~~~~~
+
+    TBD