KolabMailAccess: allocate mem for strans function pointers
KolabMailAccess: allocate mem for strans function pointers

* ISO C forbids conversion of function pointer to object pointer type
  (there's no guarantee that a function pointer will always
  fit into a void*)
* therefore, we need to explicitly allocate some memory
  via a struct containing the function pointer as a member,
  which we can then stuff into a GHashTable

GNOME/evolution-kolab,GNOME/evolution-kolab