Try to fix #1707

Current did not work on the client - `find`/`findOne` returned `undefined`:
```js
var coll = new Meteor.Collection("test");
coll.insert({title: "foo"});

coll.findOne({$or: [{title: {$in: [/foo/]}}]}); // returned undefined
on client
```

`EJSON.equals` does a correct 1:1 compare resulting in:
```js
EJSON.equals("foo", "foo"); // True
EJSON.equals(/foo/, /foo/); // True
EJSON.equals(/foo/, "foo"); // False
```
So the change is applied to `LocalCollection._f._equal` as a simple
test if `operandElt` is a regex - *Not sure if we should crawl `b` in
`_equal` (in case of an object)*