"use strict" mode wherever possible, fix #164

i think i tested everything still works thoroughly, but if not, we can fix in a followup..

also, i'm not sure these are all (and only) files we want to "use strict" in? i'm assuming we don't wanna patch libs used, but i'm not sure i identified everything what should be considered a lib, and what is a "part" of this project..

@mozfreddyb r?