sql: EXTRACT has a behavior inconsistent with pg and mysql

[knz]

See: http://www.postgresql.org/docs/8.2/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

"milliseconds: The seconds field, including fractional parts, multiplied by 1000. Note that this includes full seconds.

       SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5');
       Result: 28500

"

Our code only returns the fractional part.

Found while working on #4036.

[knz]

So the situation is actually messier than that; PostgreSQL reports the seconds together with millis/micros, but MySQL reports only the fractional part. Humpf. Will look at a middle road.