Don't handle worker tasks in the main thread.
Don't handle worker tasks in the main thread.

The handleWorkerTasks task was probably added to handle the exit flag, but worker tasks are definitely only supposed to be executed in worker threads. This change restricts the main thread to watching the exit flag.

nathanchristenson/vibe.d,Yoplitein/vibe.d,Yoplitein/vibe.d,veelo/vibe.d,Yoplitein/vibe.d,DBankov/vibe.d,schuetzm/vibe.d,mfrischknecht/vibe.d,etcimon/vibe.d,fast4shoot/vibe.d,alphaKAI/vibe.d,Kozzi11/vibe.d,alphaKAI/vibe.d,sigod/vibe.d,Mihail-K/vibe.d,gedaiu/vibe.d,sigod/vibe.d,Geod24/vibe.d,ColdenCullen/vibe.d,AndreyMZ/vibe.d,etcimon/vibe.0,machindertechnologies/vibe.d,etcimon/vibe.0,rejectedsoftware/vibe.d,nathanchristenson/vibe.d,redstar/vibe.d,yannick/vibe.d,alphaKAI/vibe.d,chalucha/vibe.d,sigod/vibe.d,etcimon/vibe.d,nathanchristenson/vibe.d