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/code/test_assertion.py

@@ -136,7 +136,7 @@ class TestView:
 
     def setup_class(cls):
         try:
-            from py.__.code._assertionold import View
+            from _py.code._assertionold import View
         except ImportError:
             py.test.skip("requires the compile package")
         cls.View = View