Update examples of the custom mutator

- Merge `examples/python_mutators` into `examples/custom_mutators`
- Remove `examples/python_mutators`
- Update existing examples to demonstrate new APIs

examples/custom_mutators/common.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+# encoding: utf-8
+'''
+Module containing functions shared between multiple AFL modules
+
+@author:     Christian Holler (:decoder)
+
+@license:
+
+This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+@contact:    choller@mozilla.com
+'''
+
+from __future__ import print_function
+import random
+import os
+import re
+
+
+def randel(l):
+    if not l:
+        return None
+    return l[random.randint(0, len(l)-1)]
+
+
+def randel_pop(l):
+    if not l:
+        return None
+    return l.pop(random.randint(0, len(l)-1))
+
+
+def write_exc_example(data, exc):
+    exc_name = re.sub(r'[^a-zA-Z0-9]', '_', repr(exc))
+
+    if not os.path.exists(exc_name):
+        with open(exc_name, 'w') as f:
+            f.write(data)