* refined braces to enable permanent braces (also in indentation-based syntax)

questions)

the implementation inherits from the brace-based implementation and
overrides the delimiters with indentation-based ones as a proof of
concept

for the transformation as target to work properly, it requires a more
sophisticated formatter that can ensure the indentation is set correctly

currently only indentation -> braces|xmi works correctly (possibly also
tdlan), not the other way around