add outer alloc image for low memory device

[HassenLin]

few code add for outer alloc image for low memory device

[dlbeer]

Apologies for the late reply. I agree that this functionality is useful, and there has been some discussion previously about adding this as a feature (see https://github.com/dlbeer/quirc/issues/119).

Unfortunately the issues preventing this request from being merged are:

• There are no commit messages beyond "Update ...". It would probably be better to squash the history into a single commit with a description of the changes.
• This breaks ABI compatibility by changing the parameters to an existing function.

If you're able to come up with something that resolves those issues (perhaps also reviewing the discussion above), then we can probably consider merging it.