TIM COCKS WHITE  South African farmers and rival Black protesters have demonstrated and came close to a full-scale clash in the Free State farming town of Senekal over a murder case that has reignited racial tensions still simmering 26 years after the end of apartheid. The killing of Brendan Horner, a white man whose body was found tied to a pole at his farm in Free State province, sparked riots at the start of this month, and prompted President Cyril Ramaphosa to make a statement urging South Africans to "resist attempts... to mobilise communities along racial lines". The farmers, who…