devel/libburn: Update to 1.5.6
Major changes:
- Bug fix: Overburning with cdrskin option -force ended by a libburn error
- New API call burn_write_opts_set_bdr_obs_exempt()
- New cdrskin option --bdr_obs_exempt
- Officially enabled overburning with burn_write_opts_set_force(,1)
Full changelog: https://dev.lovelyhq.com/libburnia/libburn/src/branch/master/ChangeLog
Port changes:
- Update WWW url
- Reorder Makefile to make linters happy