FreeTDS Needs to Support SQL Azure

[daviddoliver]

SQL Azure does not support "use" to switch between db's.

Need to replace dbuse with dbsetlname/dbopen.

// CORRECT for Azure: set DB in login record via DBSETLNAME
DBSETLNAME(login, database, DBDBNAME);
// then dbopen() — do NOT call dbuse() afterward
DBPROCESS *conn = dbopen(login, server);
// remove any dbuse(conn, database) call here