Major improvements

• Haskell: layout keywords can now be stacked on the same line [#354],
  see https://bnfc.readthedocs.io/en/latest/lbnf.html#stacking-layout-keywords
• C: new methods free_* and clone_* to deallocate and clone syntax trees [#348]
• C/C++ backends now create reentrant parsers [#349]

Bug fixes and small improvements

• Haskell-GADT: generated code is warning free [#346]
• Haskell: fixes in layout preprocessor [#343,#344,#345,#352,#353]
• Haskell: print [Char] correctly, removed method prtList [#359]
• Haskell: added missing import [#368], regression introduced in 2.9.1 by [#331]
• C: fixed a space leak when parsing from a string in memory [#347]
• C: removed errorneous defined constructors from Skeleton.c
• C++: defined constructors now reside in Absyn [#287]
• Java: defined constructor now reside in AbsynDef.java [#287]
• Ocaml: fixed translation of nested defined constructors
• C/C++/Java: Pre/post/mixfix lists are now printed correctly [#358]
• all: defined constructors involving list expressions work now [#363]
• all: printers render braces on their own line [#366]

Cosmetical changes

• C/C++: instead of _SYMB_nnn, more readable token names in lexer & parser