Another potential fix related to the recent test/format changes:
We have had two issues related to compatibility-test-for-newer-releases on Compatibility tests, see here and here.
The error is:
Seems that the off value is not correctly interpreted for btree.prefix_len. I had a quick look at config_def.c and I believe we are missing the C_BOOL variable if we want off to be correctly interpreted. However, if we do this, it means we could do btree.prefix_len=on and things would work while... it might not make sense.
Instead we may want to edit the BC_CHECK macro here so it sets the btree.prefix_len to 0 instead of off when it needs to be disabled.