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

_py/code/oldmagic2.py

@@ -0,0 +1,6 @@
+
+import py
+
+py.log._apiwarn("1.1", "py.magic.AssertionError is deprecated, use py.code._AssertionError", stacklevel=2)
+
+from py.code import _AssertionError as AssertionError