Support error codes in emitter
Support error codes in emitter

switchinnovations/pxt,Microsoft/pxt,switch-education/pxt,switch-education/pxt,playi/pxt,switch-education/pxt,Microsoft/pxt,switch-education/pxt,playi/pxt,Microsoft/pxt,playi/pxt,switch-education/pxt,Microsoft/pxt,switchinnovations/pxt,playi/pxt,Microsoft/pxt,switchinnovations/pxt,switchinnovations/pxt