* leap-seconds.list: New version 3629404800 from NIST,
fixing a commentary typo and removing trailing white space.
* Makefile (check_white_space): Remove special case for
leap-second.list.
* leap-seconds.list: Per IERS Bulletin C49 (2015-01-05), a positive leap
second will be inserted into the UTC time scale at the end of
2015-06-30. Update file from NIST, retrieved from
<ftp://time.nist.gov/pub/leap-seconds.3629404800>.