sqlquerypp issues a parser state transition when it sees ( and ).

This is correct behavior, but NOT when we are within the { ... } scope, because within that scope ( and ) are evaluated in MySQL, not sqlquerypp. Otherwise, sqlquerypp tries to unroll the state back to the combinator expression and the confusion is confused.

This led to errors when extending a sqlquerypp-preprocessed query which previously contained AND something = 'foo' to AND something IN ('bar', 'foo').

The fix is quite simple: introducing a new state variable and skipping the TokenState::OpeningParenthese transition in case we are already within the { ... } scope which contains the SQL query to combine.