merging the new function generators, addresses issue 2

- introduce a new pytest_genfuncruns hook for generating tests with multiple funcargs
- new and extended docs: doc/test/funcargs.txt
- factor all funcargs related code into py/test/funcargs.py
- remove request.maketempdir call (you can use request.config.mktemp)

--HG--
branch : trunk

py/test/testing/test_pickling.py

@@ -34,9 +34,9 @@ class ImmutablePickleTransport:
         p2config._initafterpickle(config.topdir)
         return p2config
 
-class TestImmutablePickling:
-    pytest_funcarg__pickletransport = ImmutablePickleTransport
+pytest_funcarg__pickletransport = ImmutablePickleTransport
 
+class TestImmutablePickling:
     def test_pickle_config(self, testdir, pickletransport):
         config1 = testdir.parseconfig()
         assert config1.topdir == testdir.tmpdir