Merge: tests: add test_sort_perf.nit

This test illustrate a current issue with string comparisons.
On my machine, a valgrind of it gives 80+% on BOX_Byte.

Pull-Request: #1838
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>

tests/sav/test_sort_perf.res

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+Usage: ./test [-q] paths

tests/sav/test_sort_perf_args1.res

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+test_prog/
+|--test_prog/README.md
+|--test_prog/game
+|  |--test_prog/game/README.md
+|  `--test_prog/game/game.nit
+|--test_prog/platform
+|  |--test_prog/platform/README.md
+|  `--test_prog/platform/platform.nit
+|--test_prog/rpg
+|  |--test_prog/rpg/README.md
+|  |--test_prog/rpg/careers.nit
+|  |--test_prog/rpg/character.nit
+|  |--test_prog/rpg/combat.nit
+|  |--test_prog/rpg/races.nit
+|  `--test_prog/rpg/rpg.nit
+`--test_prog/test_prog.nit

tests/test_sort_perf.args

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+test_prog/

tests/test_sort_perf.nit

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+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# 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.
+
+import ordered_tree
+
+var quiet = false
+
+var tree = new OrderedTree[String]
+var todo = new Array[String]
+if args.is_empty then
+	print "Usage: ./test [-q] paths"
+	exit -1
+else
+	if args.first == "-q" then
+		args.shift
+		quiet = true
+	end
+	todo.add_all args
+	for a in args do tree.add(null, a)
+end
+while todo.not_empty do
+	var file = todo.pop
+	var entries = file.files
+	for entry in entries do
+		var sub = file / entry
+		todo.add sub
+		tree.add(file, sub)
+	end
+end
+tree.sort_with(alpha_comparator)
+
+if not quiet then tree.write_to(stdout)