Add `TRAP 2`. A system call to print a unicode string of characters & ' character allowed in labels.

This was on the slides of the codegen lecture, but it was not actually implemented in the virtual machine.

Add ' as valid character at the start of labels. This is useful for label names that the programmer probably can not create in your language but do need to be labels. So with a ' at the start you can prevent overlap between programmer defined things and things created by your code generator. In your language variable names and or function names are probably not allowed to start with a '.