Fix #196. Errorneus tail-optimization of inner DefDef's
Fix #196. Errorneus tail-optimization of inner DefDef's

Unless a DefDef is a result of desugaring an exception handler it shouldn't be optimized by tailrec.

There's a potential improvement here: to detect that a DefDef
 is a label def which itself is called only in tail position.

 This is a requirement to implement #194

sjrd/dotty,dotty-staging/dotty,yusuke2255/dotty,folone/dotty,sjrd/dotty,svalaskevicius/dotty,angi2/dotty,dotty-staging/dotty,auvik/dotty,dotty-staging/dotty,VladimirNik/dotty,som-snytt/dotty,som-snytt/dotty,lampepfl/dotty,AlexSikia/dotty,angi2/dotty,spetz911/dotty,lampepfl/dotty,svalaskevicius/dotty,yusuke2255/dotty,lampepfl/dotty,reactormonk/dotty,auvik/dotty,sjrd/dotty,densh/dotty,som-snytt/dotty,som-snytt/dotty,vsalvis/dotty,spetz911/dotty,folone/dotty,som-snytt/dotty,VladimirNik/dotty,reactormonk/dotty,sjrd/dotty,vsalvis/dotty,AlexSikia/dotty,dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty,sjrd/dotty,densh/dotty,lampepfl/dotty