rewrote the initpkg mechanism and moved py lib implementation files to

_py/...  with py/__init__.py containing pointers into them

The new apipkg is only around 70 lines of code and allows
us to get rid of the infamous "py.__." by regular non-magical
"_py." imports. It is also available as a separately installable
package, see http://bitbucket.org/hpk42/apipkg

--HG--
branch : trunk

testing/pytest/test_config.py

@@ -107,7 +107,7 @@ class TestConfigAPI:
         py.test.raises(KeyError, 'config.getvalue("y", o)')
 
     def test_config_getvalueorskip(self, testdir):
-        from py.__.test.outcome import Skipped
+        from _py.test.outcome import Skipped
         config = testdir.parseconfig()
         py.test.raises(Skipped, "config.getvalueorskip('hello')")
         verbose = config.getvalueorskip("verbose")
@@ -229,7 +229,7 @@ class TestOptionEffects:
 
 class TestConfig_gettopdir:
     def test_gettopdir(self, testdir):
-        from py.__.test.config import gettopdir
+        from _py.test.config import gettopdir
         tmp = testdir.tmpdir
         assert gettopdir([tmp]) == tmp
         topdir = gettopdir([tmp.join("hello"), tmp.join("world")])
@@ -238,7 +238,7 @@ class TestConfig_gettopdir:
         assert gettopdir([somefile]) == tmp
 
     def test_gettopdir_pypkg(self, testdir):
-        from py.__.test.config import gettopdir
+        from _py.test.config import gettopdir
         tmp = testdir.tmpdir
         a = tmp.ensure('a', dir=1)
         b = tmp.ensure('a', 'b', '__init__.py')