Base '+' (one or more repetitions) on '*' (zero or more repetitions).

Base '+' (one or more repetitions) on '*' (zero or more repetitions).

Kleene star '*' (aka iteration, repetition, etc.) is a primitive
operation in regular expressions.

For some reason re2c used '+' as a primitive operation and expressed
'*' in terms of '+'. It is inconvenient, because all algorithms
described in literature are based on '*'.

Because we now express 'a+' as 'a* a', we have to set 'PRIVATE' attribute
on 'a': otherwize 'a' gets shared between the two occurences which causes
complex bugs.

Expressing 'a+' in a more intuitive way as 'a a*' rather than 'a* a'
causes the generated code to duplicate certain states. The generated code
is (supposedly correct), but re2c fails to deduplicate these states.
We therefore prefer 'a* a' expansion, which results in exactly the same
code as before.