Transaction vtable includes uncallable get_mergeinfo

Hello all,

I notice that txn_vtable_t includes a get_mergeinfo() function that was
(presumably) intended to retrieve all the mergeinfo set by a given
transaction (or something like that). Anyway, it's currently unused --
there's no way to call that vtable entry.

Is it intended for some yet-to-be-written mergeinfo functionality, or is
it vestigal? If the latter, I'd like to remove it (that, or fix the
implementation in FSFS, which can now throw ENOENT errors that I doubt
were intended).

Regards,
Malcolm