- changed multiplicity of mixin, object-mixin, filter, object-filter from 1..n to 0..n; rationale: when one has a list of eg. mixins, which should be passed, one has to test for the length before passing it, otherwise the empty list would generate an error. Allowing 0..n makes the usage simpler and the program shorter.
nsf.c - fixed potential inifinite loop in pattern matching for precedence lists - cget: make error message closer to tcl conventions - extended regression test