mdbx: avoid on-stack allocation/chkstk inside mdbx_check4nonlocal().
mdbx: avoid on-stack allocation/chkstk inside mdbx_check4nonlocal().

6 of 17 for https://github.com/leo-yuriev/libmdbx/issues/43

Change-Id: Ib55a27c4859ff25e5b779a4514cd2e625ab99013

leo-yuriev/libfpta,leo-yuriev/libfpta