fixes #987 fallback to localStorage.DEBUG if debug is not defined (#988)

Author: lzilioli

src/browser.js

@@ -219,7 +219,7 @@ function save(namespaces) {
 function load() {
 	let r;
 	try {
-		r = exports.storage.getItem('debug');
+		r = exports.storage.getItem('debug') || exports.storage.getItem('DEBUG') ;
 	} catch (error) {
 		// Swallow
 		// XXX (@Qix-) should we be logging these?