/*
 * call-seq:
 *    CPU.model
 *
 * Returns a string indicating the cpu model.
 *--
 * On OSX I use the hw.cputype instead of hw.model because OSX returns the
 * machine model instead of the cpu model for some reason. Initial attempts
 * to add the cpusubtype as well were unreliable.
 */
static VALUE cpu_model(VALUE klass){