[trac1104] pre-work refactoring: move the actual C++ binding of the DNS ACL

to a "hidden" _dns module with a frontend .py module.  It will make it easier
to handle objects defined in pydnspp.  no functional change at this moment.
note that we need to allow classes in the module to be subclassed.

src/lib/python/isc/acl/_dns.py

@@ -0,0 +1,33 @@
+# Copyright (C) 2011  Internet Systems Consortium.
+#
+# Permission to use, copy, modify, and distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SYSTEMS CONSORTIUM
+# DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
+# INTERNET SYSTEMS CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
+# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
+# FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
+# WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+# This file is not installed. The log.so is installed into the right place.
+# It is only to find it in the .libs directory when we run as a test or
+# from the build directory.
+# But as nobody gives us the builddir explicitly (and we can't use generation
+# from .in file, as it would put us into the builddir and we wouldn't be found)
+# we guess from current directory. Any idea for something better? This should
+# be enough for the tests, but would it work for B10_FROM_SOURCE as well?
+# Should we look there? Or define something in bind10_config?
+
+import os
+import sys
+
+for base in sys.path[:]:
+    bindingdir = os.path.join(base, 'isc/acl/.libs')
+    if os.path.exists(bindingdir):
+        sys.path.insert(0, bindingdir)
+
+from _dns import *