* modules1: (initial release)
  - fields_list given random access. More convenient than previously used
    linked lists.
  - Big code reorganisations:
    - db_access.[ch] contains the common interface to access the database
      from abook and the filters.
    - database.[ch] is for more "internal" code.
    - filter.c now only contains the code for calling import/export filters.
    - code of the filters themselves splitted from filter.c to
      filters/*_filter.c
    - interface beetween filters and abook in filters/filter_interface.h
    - helpers to easily write new modules.
  - Each filter is a module dynamically loaded when needed.
  - libltdl embedded for systems where it is not already installed.
  - Native abook format is handled through a filter module like any other
    format.

* modules2:
  - fixed "cast from pointer to integer of different size" reported by Jaako

* modules3:
  - attempt to fix included libintl build (build broken on OSX reported by
    Mark Zugsmith)

* modules5:
  - fixed segfault while leaving import/export filter selection screen
  - added code to debug listing module entries on OSX
  - preliminary 'external filter code'