Use `window.self` for both browser and web workers
Use `window.self` for both browser and web workers

It turns out that there doesn't need to be a seperate if branch for web
workers since `self` is pretty much the equalivant of `window` for browsers.
It seems that IE supports this feature as well as the other modern browsers,
so it's pretty safe to switch to this.

aurusov/highlight.js,Sannis/highlight.js,aurusov/highlight.js,carlokok/highlight.js,isagalaev/highlight.js,teambition/highlight.js,StanislawSwierc/highlight.js,highlightjs/highlight.js,StanislawSwierc/highlight.js,tenbits/highlight.js,bluepichu/highlight.js,dbkaplun/highlight.js,MakeNowJust/highlight.js,dbkaplun/highlight.js,tenbits/highlight.js,lead-auth/highlight.js,Sannis/highlight.js,carlokok/highlight.js,palmin/highlight.js,isagalaev/highlight.js,bluepichu/highlight.js,sourrust/highlight.js,highlightjs/highlight.js,sourrust/highlight.js,palmin/highlight.js,teambition/highlight.js,teambition/highlight.js,bluepichu/highlight.js,carlokok/highlight.js,palmin/highlight.js,aurusov/highlight.js,MakeNowJust/highlight.js,highlightjs/highlight.js,sourrust/highlight.js,tenbits/highlight.js,highlightjs/highlight.js,dbkaplun/highlight.js,carlokok/highlight.js,MakeNowJust/highlight.js,Sannis/highlight.js