* Clean-up now unnecessary backward propagation in comp.el

* Clean-up now unnecessary backward propagation in comp.el

	* lisp/emacs-lisp/comp.el (comp-passes): Invoke 'comp-propagate'
	instead of 'comp-propagate-alloc'.
	(comp-mvar): Remove unnecessary `array-idx' slot.
	(comp-propagate-prologue): Remove.
	(comp-propagate-prologue): Remove `backward' parameter and
	backward propagation logic.
	(comp-propagate1): Remove and move logic into `comp-propagate'.
	(comp-propagate-alloc): Remove pass.