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
Cisco optimization for x86 & fixed point

1. Only for fixed point on x86 platform (32bit and 64bit, uses SIMD
   intrinsics up to SSE4.2)
2. Use "configure --enable-fixed-point --enable-intrinsics" to enable
   optimization, default is disabled.
3. Official test cases are verified and passed.

Signed-off-by: Timothy B. Terriberry <tterribe@xiph.org>
Fix build bustage from c95c9a048.
There are no tabs in source code.

There is also no trailing whitespace.
Update mp4 encapsulation spec to v0.5.3.

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