tzcode1998e.tar.gz and tzdata1998e.tar.gz

The files ftp://elsie.nci.nih.gov/pub/tzcode1998e.tar.gz and ftp://elsie.nci.nih.gov/pub/tzdata1998e.tar.gz are now available. The Makefile is changed to produce zoneinfo-posix rather than zoneinfo/posix, and to produce zoneinfo-leaps rather than zoneinfo/right. The data changes recently circulated by Paul Eggert on the time zone mailing list are incorporated, as are the changes from Guy Harris to provide asctime_r and ctime_r. And a usno1998 file (substantially identical to usno1997) has been added. --ado