* fixed/added the overriding of unqualified impored functions by definitions of functions.
   (it was already allowed accidently but lead to wrong js being generated..)
 * prohibited the appearance of EXTERN DEF without FUN.
 * some changes to existing modules
 * tried to reactivate koch example. (koch2 does not lead to any output? :/ )
added pair and real to libs. (not really tested yet)
the real module is interesting as it overrides the operators from prelude.