Mark some stuff as const

Meh. If we ever turn on Closure's ADVANCED_OPTIMIZATIONS, it can inline
the constants and stuff.
Keep the 'use strict' when minifying

Also make winchan.js strict-clean.
Update winchan.js from upstream

Now comes from fd3a5350bf042aef245d6141b3a2dd0507097ee0 with strict-mode
fix.