Log Message:
Update to 1.4.24.

Changelog:
Version 1.4.24:
- Remove the unmaintained pt_BR translation.
- Simplify manual license: use a simple permissive license instead of GNU FDL.
- Replace a call to gnutls_protocol_set_priority(), which is deprecated in
  GnuTLS >= 2.12.0. Fixes Debian bug #624048 (reported for mpop).
- Remove gnulib, for simplicity and maintainability.
- Update GNU autotools files, in particular configure.ac.