1. Removed an inappropriate normative MAY.
2. Gave an explicit range of sample rates deemed to be "non-crazy".
3. Give explicit guidance on packet sizes that SHOULD and MAY be rejected.

This is just a should, so we want to leave the RFC 6716 reference
to the second occurance, but using the same language ties them
together and to the later occurances.

The Opus RFC doesn't really say what to do beyond rejecting
a particular packet, but having the reference reinforces that
we're trying to leverage the same constraints in the specific
context of ogg encapsulation, and this isn't a new rule.

Suggestion from mark4o.

This avoids confusion with the number of frames being defined
by more than the first byte with code 3 packets.

Patch from mark4o.

The macros take arguments, they aren't just constants. Thanks to
mark4o for the report.

Add a limit of no more than 6 characters for these tags' values.

Based on http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html

There is also no trailing whitespace.

This is a quick script to download, rename and sanitize
Yusuke Nakamura's draft for opus in the ISO Base Media File Format.

Based on http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html

SHOULD or SHOULD NOT. There is no attempt.

From the codec wg mailing list thread
https://www.ietf.org/mail-archive/web/codec/current/msg03107.html

Based on http://vfrmaniac.fushizen.eu/style.css

From http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html

Based on http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html

These are normative whether capitalized or not. Capitalize the ones
which make sense as normative requirements, and reword the rest.

We want to general guidelines for stream-level encapsulation to
apply to multiplexed as well as degenerate streams. 'Files' can
therefore specific to the mine-type discussion for unmultiplexed
Ogg physical streams.

These are the changes proposed in
 <http://www.ietf.org/mail-archive/web/codec/current/msg03058.html>,
 with some minor additions (see follow-up on the list).

Promote the new tag definitions to a separate subsection,
balance tags, improve wording, and document our motivation
for the R128 tags.

Thanks to Calvin Walton for pointing this out.