Annotate functions that are aliases for goog functions

Without the `@function` annotation, JSDoc assigns [`ol.inherits`](http://ol3js.org/en/master/apidoc/ol.html#inherits), [`ol.events.condition.always`](http://ol3js.org/en/master/apidoc/ol.events.condition.html#always), and [`ol.events.condition.never`](http://ol3js.org/en/master/apidoc/ol.events.condition.html#never) as "members" instead of "functions."  The distinction means they are grouped separately in the docs.  Adding the `@function` annotation groups them with other functions we create in the lib.

In addition, this adds documentation for `ol.inherits` (cribbed from the goog docs).