doc-rst: make dev-tools folder buildable stand-alone

Add minimal conf.py and moved dev-tools/tools.rst to dev-tools/index.rst
makes the dev-tools folder buildable stand-alone. To build only this
folder run::

  make SPHINXDIRS=dev-tools htmldocs
  make SPHINXDIRS=dev-tools pdfdocs

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst
new file mode 100644
index 0000000..07d8811
--- /dev/null
+++ b/Documentation/dev-tools/index.rst
@@ -0,0 +1,33 @@
+================================
+Development tools for the kernel
+================================
+
+This document is a collection of documents about development tools that can
+be used to work on the kernel.  For now, the documents have been pulled
+together without any significant effot to integrate them into a coherent
+whole; patches welcome!
+
+.. class:: toc-title
+
+	   Table of contents
+
+.. toctree::
+   :maxdepth: 2
+
+   coccinelle
+   sparse
+   kcov
+   gcov
+   kasan
+   ubsan
+   kmemleak
+   kmemcheck
+   gdb-kernel-debugging
+
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`