Bug#984807: Add stdmusic to freeciv-sound-standard package

[Marko Lindqvist]

Package: freeciv-sound-standard
Version: 2.6.3-1

In addition to the standard sound effects set, freeciv-sound-standard
package should include standard music set. In the standard music set,
there's only one track of menu music, so it's not adding a lot to the
package size.
This is also a regression since freeciv-2.5 series, since back then
there were no separate music sets, but the music was included to the
sound set. Debian used to have the menu music via the sound set.
The files belonging to the standard music set are
data/stdmusic.musicspec and content of data/stdmusic/


 - ML