Classdef takes 4 args
Added missing semicolon
Enable typechecking
Update make file
Merge branch 'lab3' of github.com:samuel02/RTFM into lab3

# By Angelica Brusell (1) and Björn Nilsson (1)
# Via Samuel Nilsson (2) and Björn Nilsson (1)
* 'lab3' of github.com:samuel02/RTFM:
  String indexing returns char
  pushing changes that got lost

Conflicts:
	RTFM-cOOre-compiler/src/Graphviz.ml
Small fixes
Remove commented code
Merge branch 'lab3' into extern
added test case for extern methods