Mysql.result: Renamed seek() to low_seek().
This function performs absolute positioning (rather than the
relative positioning of __builtin.Sql.Result()->seek()), and
was shadowed by a generic (relative) implementation in previous
versions of Pike.
CAVEAT: Old code that used sql_res->master_res->seek() will
break and need to be updated. Any such code will trigger
warnings as master_res has been declared deprecated.
It is also unlikely that any such code exists, since the
function didn't comply with its documented behavior.
Fixes some testsuite failures.