Initial implementation of manual highlighting (#1087)

* Initial implementation of manual highlighting

Borrow the `manual` property of whatever already existing Prism instance
there is.

* Simplify setting of `Prism.manual`

Cleans up the implementation w/ less code.

components/prism-core.js

@@ -19,6 +19,7 @@ var lang = /\blang(?:uage)?-(\w+)\b/i;
 var uniqueId = 0;
 
 var _ = _self.Prism = {
+	manual: _self.Prism && _self.Prism.manual,
 	util: {
 		encode: function (tokens) {
 			if (tokens instanceof Token) {
@@ -483,7 +484,7 @@ var script = document.currentScript || [].slice.call(document.getElementsByTagNa
 if (script) {
 	_.filename = script.src;
 
-	if (document.addEventListener && !script.hasAttribute('data-manual')) {
+	if (document.addEventListener && !_.manual && !script.hasAttribute('data-manual')) {
 		if(document.readyState !== "loading") {
 			if (window.requestAnimationFrame) {
 				window.requestAnimationFrame(_.highlightAll);