fixed definition handler bug: extern functions like GCD are now correctly included inside the ast.
(The first child node of a function node is not allways a idnode). no systerel-mch fail because of missing ext. funtions
extended fake_set functionality: equal. of fake sets. no systerel-mch. fail because of inf.- or large-set compare.

finally: 3 systerel mch. pass (see table)