Optimize disposal of IOVectors

[facundominguez]

As of #150, the finalizer of IOVectors resulting from marshaling Java vectors to Haskell will attach the finalizer thread to the JVM.

We could avoid that by extending the interface of the background thread we use to delete global references.

inline-java/jvm/src/common/Language/Java/Unsafe.hs

Line 560 in 87219c5

fptr <- newForeignPtr ptr $ runInAttachedThread $