GPU - extention to pass buffers with different API

# Open Effects Proposal for Standard Change

Please read the contribution [guidelines](https://github.com/ofxa/openfx/wiki/Extending-OpenFX-Guidelines#submit-a-proposal-or-bug-report-to-review) first.

## Standard Change Workflow
- [x] Create proposal as issue (you're doing this now!)
- [x] Tag this issue with `standard change` tag
- [ ] Identify subcommittee: at least one plug-in vendor, and at least one host
- [ ] Discuss the idea in this issue
- [ ] Write new or updated code and doc
- [ ] Publish updates as a pull request (ideally on a `feature/PROPOSAL-NAME` branch)
- [ ] Make sure that PR references this issue number to keep them in sync
- [ ] Discuss and review code in the PR
- [ ] Meet all requirements below for accepting PR
- [ ] When subcommittee signs off and other members don't have any further review comments,
maintainer merges PR to master which closes PR and issue

## Requirements for accepting a standard change:
- [ ] Header files updated
- [ ] Documentation updated
- [ ] Release notes added
- [ ] Compatibility review completed
- [ ] Working code demonstrated with at least one host and one plugin
- [ ] At least two members sign off
- [ ] No further changes requested from membership

## Summary

Describe the change succintly in one or two sentences.

## Motivation

Why is this change proposed?

## Problem

What problem does this proposed change solve? Be specific, concise, and clear.

## Impact

Is this a new feature (no compatibility impact), a change to an existing function suite (version
the suite to avoid compatibility issues), a change to an existing property, or a documentation
change?

How will hosts and plugins negotiate use of this change? Show how it works when a host implements
it but not plugin and vice versa.

## Documentation Impact

What changes to the docs are needed for this change?

## Stakeholders

Who will benefit from this proposed change? Plug-ins, hosts, or both? Specific types of hosts?

## Discussion

Start with the contribution guidelines linked in the issue and review the standard change workflow and acceptance requirements. The proposal fields for summary, motivation, problem, impact, documentation impact, stakeholders, and discussion are still empty, so the intended buffer API change and its completion criteria are not defined; linked pull request #101 is closed.

Written by the indexing model from the issue text.