Marked code that will require some rework for LMDB.

Marked code that will require some rework for LMDB.

When BDB returns data, the caller owns the memory and is required to
free it, which we usually do.  I marked the places where we take ownership
of memory pointers and then set the BDB ptr to NULL.  If we switch to
LMDB, those pointers remain valid forever, so we cannot simply free them
later.