atk rbatkutil.c: drop #if ATK_CHECK_VERSION(1,6,0)
atk rbatkrelation.c: drop #if ATK_CHECK_VERSION(1,9,0)
atk rbatkrelationset.c: drop ATK_CHECK_VERSION(1,9,0)
atk rbatkdocument.c: drop ATK_CHECK_VERSION(1,12,0)
atk rbatkcomponent.c: drop ATK_CHECK_VERSION(1,12,0)
add required libatk version