Firefox 54 compatiblity for locale service

Services.locale.getApplicationLocale() -> getAppLocale()
(nsILocaleService -> mozILocaleService)

It's possible this will fix some of the locale resolution problems in
Standalone:

"This is actually a meaningful change because the old one was actually
using OS locale for platforms other than Windows. The new one is using
the app locale for all platforms." [1]

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1346674#c0

chrome/content/zotero/xpcom/zotero.js

@@ -242,7 +242,13 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 		}
 		
 		// Load in the localization stringbundle for use by getString(name)
+		if (Services.locale.getAppLocale) {
+			var appLocale = Services.locale.getAppLocale();
+		}
+		// Fx <=53
+		else {
 			var appLocale = Services.locale.getApplicationLocale();
+		}
 		
 		_localizedStringBundle = Services.strings.createBundle(
 			"chrome://zotero/locale/zotero.properties", appLocale);