[fitsbits] FITS reference

[Malcolm Currie]

I'd prefer a slightly longer version.

COMMENT   FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT   and Astrophysics' vol 376, page 359; bibcode 2001A&A...376..359H.

The extra line helps it stand out, and the expansion of the acronym will
give non-astronomers a clue as to what it is.

URLs change, and can be longer than the 70 characters available, so
I'm lukewarm to include one of those.

To answer Don, the Starlink FITS writer uses CFITSIO, so we'll have
whatever Bill decides.  At UKIRT, our header-definition tables include
the current CFITSIO comments.  I'll be changing them shortly to reflect
the new reference.

Malcolm Currie
Joint Astronomy Centre