Bug#922817: neon library variant no longer installed, ARM performance regression

[Daniel Drake]

Package: libvpx
Version: 1.6.1-3+deb9u1

In Debian Jessie, ARM VP9 decoding was working well on many platforms
thanks to the neon library additionaly provided at
/usr/lib/arm-linux-gnueabihf/vfp/neon/libvpx.so.1.

However, as of Debian Stretch (and also in Debian Buster), the neon
library variant is no longer installed by the package, so the system
falls back on the "generic" version, where the decoding performance is
very noticably worse. On Endless Mini (Amlogic S805) this makes most
videos unwatchable due to excessively low framerate.

The bug is that the entry in libvpx{4,5}.install for the neon variant
ends with the [arm] arch selector, but this should actually be [armhf
armel] in order for the file to be included in the installation.