Updated: libvpx-utils/-doc/-devel, libvpx8 1.13.1-2

[Cygwin libvpx Maintainer]

The following packages have been upgraded in the Cygwin distribution:

* libvpx-utils		1.13.1-2
* libvpx-doc		1.13.1-2
* libvpx-devel		1.13.1-2
* libvpx8		1.13.1-2

Google WebM VP8/VP9 video graphics codecs encoders and decoders
library reference implementation.

For more information see the project home page:

	https://github.com/webmproject/libvxp/

This Cygwin release reduces the installed size by over 1.5MB and:

* generates utility man pages with help2man
* installs basic docs with the runtime library package
* limits exported symbols with a version script generated from sources
* builds the shared library with pic and the version script
* installs test data in an out of tree cache directory to avoid
  1.4GB re-downloads every rebuild.