determine what can be done about the polyfills that were re-hidden in r28

[DanAlbert]

Description

https://github.com/android/ndk/issues/2081 reported issues with the blanket exposure of all the stuff previously hidden by versioner. We've rehidden those things behind __ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__, but it'd be nice to be able to re-expose the polyfills even outside that mode since those should make things better for everyone. At least one library (libconfuse) had issues with that though. Someone will need to go and figure out why so we can determine if adding unconditional polyfills is something we can pursue or not.