Imported Upstream version 2.3
Merge tag 'upstream/2.3'

Upstream version 2.3
update patches
update symbols files
update ffmpeg.lintian-overrides
include config.log in the build-log, when configure fails
add libgnutls28-dev build-dependency
install the release notes into /usr/share/doc/ffmpeg
add build-dependencies and enable in debian/rules: libbs2b, libfribidi
update debian/copyright
update changelog
fix pkg-config_file_without_build_suffix.patch and update offsets of other patches
update dependencies of -dev packages
update changelog
use packaged libjs-jquery instead of the jquery created by doxygen
fix spelling errors
update changelog