* gnu/packages/music.scm (extempore): Update to 0.8.6.
[snippets]: Delete bundled dependencies.
[patches]: Add it.
* gnu/packages/patches/extempore-unbundle-external-dependencies.patch: Patch
CMakeLists.txt to use system libraries.
* gnu/local.mk (dist_patch_DATA): Add it.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
