* Arabtec plunges as Aabar remains secretive * Dubai property price growth slows, report says * Saudi's Dar Al Arkan, SIIG results miss estimates * Qatar's Al Khaliji bank also drops on Q2 earnings * Kuwait's KIPCO rises after OSN offer By Olzhas Auyezov DUBAI, July 20 (Reuters) - Dubai's stock market plunged on Sunday as builder Arabtec triggered a**ther sell-off, while investors in Saudi Arabia and Qatar were disappointed by fresh quarterly earnings reports. ...