mediawiki.js request() caching deep level object member access.

mediawiki.js request() caching deep level object member access.
- Instead of requesting index 0 of dependancies-argument, and the value of that of the registry, and the dependancies object in that of which we read the length property is very deep. Even worse when doing that both in the head and in the body of a for()-loop.
- Instead caching reference access to dependancies object of the registry item.
- Plus a simple by-value of the length property