Software specialist Adobe Systems has reported a 41 percent increase in second-quarter profit as strong revenue growth overseas offset flat sales in the United States.   Adobe, whose brands include Photoshop, Flash and Acrobat, revealed net income in the three months to May 30 of $214.9 million, up from $152.5 million in the same quarter a year ago.    Second quarter revenue rose 19 percent to $887 million, led by a 40 percent increase in sales in Europe.