Related issue:
mdb_cursor_prev/mdb_cursor_last() with data==NULL position the
xcursor at 1st data item, while data!=NULL puts it at last item.
That's unintuitive and should either be documented or normalized -
but changing it can break existing programs. In the cases when
it didn't just fail
Full_Name: Hallvard B Furuseth
Version: mdb.master, fa83b25ec536ac2642f8e0d3c6bf587008513ef4
OS: Linux x86_64
URL: ftp://ftp.openldap.org/incoming/Hallvard-Furuseth-161201.c
Submission from: (NULL) (129.240.203.186)
Submitted by: hallvard
liblmdb can crash or give an EINVAL in some cases after
