Accomodate rename in patched code for emscripten
Accomodate rename in patched code for emscripten

They renamed `unusedWorkerPool` to `unusedWorkers`, breaking a patch
step in the Pthread build.

https://github.com/emscripten-core/emscripten/issues/8338

hostilefork/rebol,giuliolunati/ren-c,giuliolunati/ren-c,hostilefork/rebol,hostilefork/rebol,rgchris/ren-c,giuliolunati/ren-c,hostilefork/rebol,rgchris/ren-c,giuliolunati/ren-c,hostilefork/rebol,rgchris/ren-c,giuliolunati/ren-c,hostilefork/rebol,rgchris/ren-c,rgchris/ren-c