Refactor of #1403: we already had a method for that
ExpressionTransformer #1402: make sure spread iterables are cast to Sequence for +variadics
Test for #1402: Sequence spread inconsitent on conditional statement
ClassTransformer #1395: make default param methods for toplevel classes be public static

Otherwise some subclass with the same parameter name defaulted may be rejected as trying
to override a static method (hah) with a more restricted access
Updated test .src for #1395: Compiler error with non-shared derived classes
Test for #1395: Compiler error with non-shared derived classes