Improve threaded handling of errno:

Improve threaded handling of errno:

- Change various incorrect direct references to errno into
  *(__errno_location()).

- In __errno_location and __h_errno_location, treat the tid==1 case
  (root thread) specially, as with __res_state().

This seems to fix a bug in threaded handling of errno on R H 9 and SuSE8.2,
and almost makes OpenOffice work again on R H 9.

MERGE TO STABLE, if it doesn't break anything.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1625