Added examples for Nit to samples.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

samples/Nit/drop_privileges.nit

@@ -0,0 +1,46 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Copyright 2013 Alexis Laferrière <alexis.laf@xymus.net>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Example using the privileges module to drop privileges from root
+module drop_privileges
+
+import privileges
+
+# basic command line options
+var opts = new OptionContext
+var opt_ug = new OptionUserAndGroup.for_dropping_privileges
+opt_ug.mandatory = true
+opts.add_option(opt_ug)
+
+# parse and check command line options
+opts.parse(args)
+if not opts.errors.is_empty then
+	print opts.errors
+	print "Usage: drop_privileges [options]"
+	opts.usage
+	exit 1
+end
+
+# original user
+print "before {sys.uid}:{sys.gid}"
+
+# make the switch
+var user_group = opt_ug.value
+assert user_group != null
+user_group.drop_privileges
+
+# final user
+print "after {sys.uid}:{sys.egid}"