Changes for SOFA Issue: 2005-09-01

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.