v0.3.6

Fixed

• sn_freelist_allocator_reallocate() split a node at new_size + align without
  first checking the node was that big, in both of its in-place paths. The
  shrink path tested the space measured from the user pointer, which does not
  cover the node header or the alignment padding ahead of it, and the extend
  path compared the merged size against new_size and left out the alignment
  reserve that sn_freelist_allocator_allocate() adds before it looks for a
  node. A node landing in the gap between the two made the subtraction in
  split_node_if_possible() underflow instead of going negative, so it split
  anyway and left a free node reaching past the end of the block, sized close
  to UINT64_MAX. That node covered whatever was allocated above it, so a later
  allocation could hand out memory another block was still using. Growing the
  three arrays of a sparse set out of one free list hit this and aborted on a
  key that came back present twice. Both paths now require the node to cover
  new_size + align and fall through to moving the block when it does not, and
  split_node_if_possible() refuses a size it cannot cover