/*
 * call-seq:
 * multi = Curl::Multi.new
 * multi.pipeline = true
 *
 * Pass a long set to 1 to enable or 0 to disable. Enabling pipelining on a multi handle will make it
 * attempt to perform HTTP Pipelining as far as possible for transfers using this handle. This means
 * that if you add a second request that can use an already existing connection, the second request will
 * be "piped" on the same connection rather than being executed in parallel. (Added in 7.16.0)
 *
 */
static VALUE ruby_curl_multi_pipeline(VALUE self, VALUE onoff) {