Bug#861928: lv2 plugin directory

[Takeshi Soejima]

Package: amsynth
Version: 1.6.4-1

Dear maintainers,

This package installes lv2 plugins to /usr/lib/x86_64-linux-gnu/lv2, but
Ardour can not scan the directory except setting "LV2_PATH" environment
variable.

Considering that Debian Policy says "a program must not depend on
environment variables to get reasonable defaults", and that most of
other packages install lv2 plugins to /usr/lib/lv2 at this moment, I
think it's better to install the plugin of this pacakge also to there.