TimestampUtils.toString() speedup

Here is a small change that improved the performance of setting a timestamp field on a prepared statement from 0.513ms to 0.083ms in our tests. Measured using JProfiler for 50,000 iterations. Essentially it is switching to use SimpleDateFormat for toString(). I believe this code is from the 8.1 408 driver.

public static final SimpleDateFormat pgdtf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssZ GG");
private static final FieldPosition FIRSTPOS = new FieldPosition(0);

public synchronized String toString(Calendar cal, Timestamp x) {
if (cal == null)
cal = defaultCal;

cal.setTime(x);
sbuf.setLength(0);

if (x.getTime() == PGStatement.DATE_POSITIVE_INFINITY) {
sbuf.append("infinity");
} else if (x.getTime() == PGStatement.DATE_NEGATIVE_INFINITY) {
sbuf.append("-infinity");
} else {

pgdtf.format(cal.getTime(), sbuf, FIRSTPOS);

/*
appendDate(sbuf, cal);
sbuf.append(' ');
appendTime(sbuf, cal, x.getNanos());
appendTimeZone(sbuf, cal);
appendEra(sbuf, cal);
*/
}

showString("timestamp", cal, x, sbuf.toString());
return sbuf.toString();
}