Clarify ambiguity between 'streams' and 'files'.

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.
Fix ambiguous RFC 2119 keywords.

These are normative whether capitalized or not. Capitalize the ones
which make sense as normative requirements, and reword the rest.
Fix mixed-case RFC 2119 keywords
Apply further fixes from Ron.
minor language tweak to RTP draft
updating the update draft
Lowered the smallest packet that the multi-stream encoder can encode

Limit now at 2*streams-1 and anything below that returns OPUS_BUFFER_TOO_SMALL
rather than OPUS_BAD_ARG
Takes into account a corner case with the multistream encoder

Considers the case where one stream would eat up all the remaining bytes,
including a 2-byte size that would then not leave enough for the even a PLC
packet in the next streams.
Fixes comments
Import mp4 encapsulation spec v0.1.4.

Based on http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html
Update mp4 encapsulation spec to v0.1.7.

From http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html
Add stylesheet for opus_in_isobmff draft.

Based on http://vfrmaniac.fushizen.eu/style.css
Add wording about additional binary data in comment headers.

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

SHOULD or SHOULD NOT. There is no attempt.
Clarify that leading '+' is allowed in R128 tags.
Update mp4 encapsulation spec to v0.4.8.

Based on http://vfrmaniac.fushizen.eu/contents/opus_in_isobmff.html
Add build script for mp4 spec.

This is a quick script to download, rename and sanitize
Yusuke Nakamura's draft for opus in the ISO Base Media File Format.
-DOPUS_WILL_BE_SLOW to disable the no-optimization warning