yieldAndThrow takes a Throwable, there's no reason for call to return an Object
fix property enforcement
fix import declarations
Merge pull request #805 from 9rnsr/enforceProp

fix property enforcement
Fix locking in GC.rootIter and GC.rangeIter
Merge pull request #806 from 9rnsr/fix12359

fix import declarations
Merge pull request #807 from Safety0ff/gciterlock

Fix locking in GC.rootIter and GC.rangeIter
applying the same change to thread.di
Merge pull request #804 from complexmath/fixCallReturnType

Change Fiber.call to return a Throwable