By Daren Butler and Humeyra Pamuk ISTANBUL/ANKARA (Reuters) - Turkish trade unionists banging drums and trailing banners marched into an Istanbul square on Wednesday, joining unprecedented protests against Prime Minister Tayyip Erdogan over what they see as his authoritarian rule. Members of more than a dozen unions chanting "Tayyip resign" marched down a major avenue towards Taksim Square. There were similar protests against Erdogan, prime minister for over 10 years and winner of three elections, in Kizilay Park in the capital Ankara. ...