[PATCH 0/3] MR7569: mfplat/tests: Add tests for Byte Stream Timestamps.

[Brendan McGrath (＠redmcg)]

This MR adds tests to `mfplat` to illustrate the timestamp values output on the samples for the respective Byte Stream handlers.

I have also included a fix for a bug in `winegstreamer` (and copied to `mfsrcsnk`) where a `NULL` value for the `pguidTimeFormat` parameter in `IMFMediaSource::Start` causes a segmentation fault. On Windows this is allowed. It is included in this MR as the `mfplat` tests pass NULL (so without this fix, the tests crash).