Street battles between rival Palestinian factions, including shootout on grounds of Gaza City hospital, leave at least five people dead and nearly 20 wounded; Hamas and Fatah security chiefs report agreement to remove gunmen from streets but effect is uncertain; Israeli Prime Min Ehud Olmert makes surprise trip to Jordan for meeting with King Abdullah on reviving peace talks; king offers to mediate among Palestinians; Egyptian diplomatsalso try to bring sides together; Hamas leader Ismail Haniya again rejects Pres Mahmoud Abbas's call for new elections (M)...