I want to use the altenate function of GPIO 4 namely the GPCLK0 function. How can one set a GPIO to its alternate function? Many alternate functions are summarized here: elinux-wiki

The best would be if it is possible with the wiringPi Library. But i do not mind to use arbitrary C-code if someone tells me how to do it. After entering an alternative function, i think it is needed to configure it?