Tag the libvorbis 1.3.3 release.

Tag the libvorbis 1.3.4 release.

Tag the libvorbis 1.3.5 release.

libvorbis 1.3.6 (2018-03-16) -- "Xiph.Org libVorbis I 20180316 (Now 100% fewer shells)"

* Fix CVE-2018-5146 - out-of-bounds write on codebook decoding.
* Fix CVE-2017-14632 - free() on unitialized data
* Fix CVE-2017-14633 - out-of-bounds read
* Fix bitrate metadata parsing.
* Fix out-of-bounds read in codebook parsing.
* Fix residue vector size in Vorbis I spec.
* Appveyor support
* Travis CI support
* Add secondary CMake build system.
* Build system fixes

libvorbis 1.3.7 (2020-07-04) -- "Xiph.Org libVorbis I 20200704 (Reducing Environment)"

* Fix CVE-2018-10393 - out-of-bounds read encoding very low sample rates.
* Fix CVE-2017-14160 - out-of-bounds read encoding very low sample rates.
* Fix handling invalid bytes per sample arguments.
* Fix handling invalid channel count arguments.
* Fix invalid free on seek failure.
* Fix negative shift reading blocksize.
* Fix accepting unreasonable float32 values.
* Fix tag comparison depending on locale.
* Fix unnecessarily linking libm.
* Fix memory leak in test_sharedbook.
* Update Visual Studio projects for ogg library filename change.
* Distribute CMake build files with the source package.
* Remove unnecessary configure --target switch.
* Add gitlab CI support.
* Add OSS-Fuzz support.
* Build system and integration updates.