(from ebtree 6.0.2) When inserting duplicates on x86/x86_64, the assembler optimization does not support equal strings that both end up with a zero, and can return garbage in the bit number, possibly causing a segfault for its users. The only case where this can happen appears to be in ebst_insert(). (cherry picked from commit 006152c62ae56d151188626e6074a79be3928858)