made a request_free() and rad_free() take a '**' pointer, instead

	made a request_free() and rad_free() take a '**' pointer, instead
	of a '*' pointer.  This allows those functions to set the input
	variable to NULL, to explicitely tell the caller it's no longer
	valid.

	It also minimizes the code, as there was a lot of:

	rad_free(foo);
	foo = NULL;