Update gcode.js to new class names
Update gcode.js to new class names

The language is unlike anyhing else in highlight.js so it's definitely
going to be wrong. For now here's some notes:

- meta, built-ins, keywords are straight-forward and correct
- line numbers (Nxxx) look like goto labels and therefore use 'symbol'
- G- and M-commands use 'name' simply because there's nothing else
  matching and defining a whole new class name for one specialized
  language is not worth it
- labels on the left side of the equal sign use 'attr' as they do
  look like attributes after all, and it's okay if they aren't colored

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