new directory 'tests/bugs' to keep tests for open tickets

test naming convention: descriptivename_Txyz.pyx, 'xyz' being the bug number in trac
when a ticket is closed, the test should be copied to 'tests/run'.

--HG--
rename : tests/unimplemented/methodmangling.pyx => tests/bugs/methodmangling_T5.pyx

tests/unimplemented/methodmangling.pyx → tests/bugs/methodmangling_T5.pyx

+# this is ticket #5
+
 __doc__ = u"""
 >>> class PyTest(object):
 ...     def __private(self): pass