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

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

Change-Id: Icff2d67f84283820fb21932c0d439d645c634d25

leo-yuriev/libfpta,leo-yuriev/libfpta