mdbx: avoid large '.data' section in mdbx_chk.
mdbx: avoid large '.data' section in mdbx_chk.

Initializes walk-array in runtime, for placing it
in the '.bss' section instead of '.data'.

Change-Id: I5bd1d9cabd2094f8ae517d91488840ce12844bfa

leo-yuriev/libfpta,leo-yuriev/libfpta