Do we really need BasicHashtableEntry<F>::next_addr() API?

For my JDK-8166145 I prototyped an optimization, that needs to be turned off whenever someone uses next_addr(), since the client might change the underlaying pointer (next_add() is not a ver apt name since it is returning a handle, and not the pointer).

I tried to modify "StringTable::buckets_unlink_or_oops_do()" not to use the next_addr() API, and only use next(), but it fails Java2Demo.jar with:

# Internal Error (../../../../hotspot/src/share/vm/gc/serial/markSweep.inline.hpp:53), pid=35902, tid=20995
# assert(Universe::heap()->is_in(obj)) failed: should be in heap, p:0x7fdd168860e0, heap_oop:0x700001758468, obj:0x6c1019e40