Should implement create_loop(autorun=TRUE)

[wch]

See here:

later/R/later.R

Lines 50 to 54 in ae297fa

	#' @param autorun Should this event loop automatically be run when its parent
	#' loop runs? Currently, only FALSE is allowed, but in the future TRUE will
	#' be implemented and the default. Because in the future the default will
	#' change, for now any code that calls \code{create_loop} must explicitly
	#' pass in \code{autorun=FALSE}.

This will eliminate the need for a callback that does the following:

• the callback schedules the private loop to run from the main loop.
• it reschedules itself.