SOFA changes implemented for the issue 2005-09-01

The following changes have been implemented for the issue 2005-09-01.

Changes

1) An error in the routine iau_SEPP (angle between two vectors) was
   corrected. For the unique case where two vectors are precise opposites, 
   the previous version returned zero instead of pi.

2) In the star-space-motion routines iau_PVSTAR and iau_STARPV, the 
   DR2AS constant was truncated rather than rounded. The correction, a 
   change by 1 in the 25th decimal digit, will have had no practical 
   consequences

3) The routine iau_DAT was updated to include the UTC leap second at 
   the end of 2005.

4) A small efficiency improvement was made to iau_C2IXYS. The results
   should be unaffected.

5) Improvements to text and layout.

IAU SOFA Center
2005-08-23