build: update sphinx tool

Use the improved version from the ndn-cxx repository

Refs: #5298
Change-Id: I681f38faa0078a67089b6a9c22eb56572a1c2940
diff --git a/.waf-tools/doxygen.py b/.waf-tools/doxygen.py
index 6d8066b..6948194 100644
--- a/.waf-tools/doxygen.py
+++ b/.waf-tools/doxygen.py
@@ -1,9 +1,6 @@
-#! /usr/bin/env python
-# encoding: UTF-8
 # Thomas Nagy 2008-2010 (ita)
 
 """
-
 Doxygen support
 
 Variables passed to bld():
@@ -27,9 +24,8 @@
 			bld(features="doxygen", doxyfile='Doxyfile', ...)
 """
 
-from fnmatch import fnmatchcase
-import os, os.path, re, stat
-from waflib import Task, Utils, Node, Logs, Errors, Build
+import os, os.path, re
+from waflib import Task, Utils, Node
 from waflib.TaskGen import feature
 
 DOXY_STR = '"${DOXYGEN}" - '
@@ -207,8 +203,8 @@
 	conf.find_program('doxygen', var='DOXYGEN', mandatory=False)
 	conf.find_program('tar', var='TAR', mandatory=False)
 
-# doxygen docs
+# doxygen command
 from waflib.Build import BuildContext
 class doxy(BuildContext):
-    cmd = "doxygen"
-    fun = "doxygen"
+    cmd = 'doxygen'
+    fun = 'doxygen'