Small changes to handle large, multi-message sysEx data transfers

[lucianthorr]

Hi. We are currently working on a project to use JUCE to handle firmware updates which require us to send large sysEx payloads that span multiple messages. In the process, we found that we needed to make a couple small changes to the JUCE library.

One change to the MidiMessage validation: We needed to allow small messages that could be the trailing end of a sysEx payload to pass the jassert

And secondly, we needed a way to force CoreMidi to use the old implementation because the new implementation does not currently handle large, multi-message sysEx payloads.

Thanks! (resubmitting because the CLA verification failed on the first try)

[lucianthorr]

I believe the web-flow author is breaking the CLA check. It's an automated attribution because one of my commits were made within the GitHub editor. Can you whitelist that name or should I start over with clean fork?