Framing Bit for comments varies

Some of the formats have a framing bit at the end of the comments, if
the comments are null padded, but not all. This makes it an option
for the implementations.
Re-enable Opus 1.1 file tests

Now that framing is marked as not present for Opus based files,
re-enable and complete the Opus tests for 1.1 files
Finish Opus 1.1 write tests
Explicit source encoding