Run post install task executing _build_tables

* Add post install task executing _build_tables in install destination
* Use distutils execute for building tables to respect dry_run flag
* Use setuptools if available, fall back to distutils if not
* Name the overriden class install to get the right help text
* Also run _build_tables when creating a source distribution
* No more need to run _build_tables.py manually

Closes #5
diff --git a/setup.py b/setup.py
index 0801f6f..605df08 100644
--- a/setup.py
+++ b/setup.py
@@ -1,5 +1,32 @@
 import os, sys
-from distutils.core import setup
+try:
+    from setuptools import setup
+    from setuptools.command.install import install as _install
+    from setuptools.command.sdist import sdist as _sdist
+except ImportError:
+    from distutils.core import setup
+    from distutils.command.install import install as _install
+    from distutils.command.sdist import sdist as _sdist
+
+
+def _run_build_tables(dir):
+    from subprocess import call
+    call([sys.executable, '_build_tables.py'],
+         cwd=os.path.join(dir, 'pycparser'))
+
+
+class install(_install):
+    def run(self):
+        _install.run(self)
+        self.execute(_run_build_tables, (self.install_lib,),
+                     msg="Build the lexing/parsing tables")
+
+
+class sdist(_sdist):
+    def make_release_tree(self, basedir, files):
+        _sdist.make_release_tree(self, basedir, files)
+        self.execute(_run_build_tables, (basedir,),
+                     msg="Build the lexing/parsing tables")
 
 
 setup(
@@ -24,6 +51,7 @@
         'Programming Language :: Python :: 3',],
     packages=['pycparser', 'pycparser.ply'],
     package_data={'pycparser': ['*.cfg']},
+    cmdclass={'install': install, 'sdist': sdist},
 )