Eo: Add a private dict which can be used for callbacks etc.

efl/eo/efl.eo.pyx

@@ -235,6 +235,7 @@ cdef class Eo(object):
 
     def __cinit__(self):
         self.data = dict()
+        self.internal_data = dict()
 
     def __init__(self, *args, **kwargs):
         if type(self) is Eo:

include/efl.eo.pxd

@@ -23,6 +23,7 @@ cdef:
         cdef:
             cEo *obj
             readonly dict data
+            dict internal_data
 
             int _set_obj(self, cEo *obj) except 0
             int _set_properties_from_keyword_args(self, dict kwargs) except 0