Merge branch 'modules-rewrite', remote-tracking branch 'origin'
Fixed exception desugar to reraise uncatched exceptions
filter test is now passing
Fixed FuncIter.__init__ to return None
Fixed default argument desugar
Only adapted the existing solution to the new scope, which makes
iter-stop.py test to pass, but only works for 1 default argument
assuming no other arguments are present, otherwise they are
silently discarded.
added clean target, rewrote typecheck target to check only files modified since last commit
moved the import desugaring into pre-lex desugar (located in python-phase1.rkt) so that scoping is handled correctly
whoops, unintentionally pre-defined scope there.  fixed.