[fitswcs] Paper III

[Eric Greisen]

I have incorporated Mark's comments as

1. Add SSYSSRCa character keyword
2. Drop VSOURCEa leaving only ZOURCEa to describe the source velocity
   - let's avoid keyword creep!
Changes are in red.

See:

      http://www.aoc.nrao.edu/~egreisen

which will always reference the latest copy.  That copy is at present

      http://www.aoc.nrao.edu/~egreisen/scs_040815.ps.gz
      http://www.aoc.nrao.edu/~egreisen/scs_040815.ps
      http://www.aoc.nrao.edu/~egreisen/scs_040815.pdf

Eric Greisen