The relax_data.delete user function is now finally properly implemented!
This was reported by Martin Ballaschk <ballaschk att fmp-berlin dott de> as bug #19785
(https://gna.org/bugs/?19785), and the mail message at
http://www.mail-archive.com/relax-users@.../msg01183.html (Message-Id:
<EED32F2B-B78F-4D23-9E0B-3DDE8B661F48@...>).
The problem was that this was not being checked by the test suite, and no one had tried to delete
relaxation data before (well, at least it was never reported).
