Support for fast array lookups in FGL
FGL supports a form of fast array lookup based on the fgarray abstract stobj. The accessors and updaters for the fgarray abstract stobj have corresponding primitive implementations in FGL that operate on real fgarray objects stored in the FGL interpreter state. As with FGL's support for fast alists (see fgl-fast-alist-support), some care must be taken to use these array objects in a single-threaded manner.