different packages per release

[dario23]

• ubuntu 17.04 has chtrt5645.conf in libasound2-data
• ubuntu 16.04's libasound2-data doesn't yet have it

so to avoid hacks like the one in gpdpocket-audio/files/DEBIAN/postinst, there could be separate packages for the different releases where the xenial one can just install the file (as it's not in the archive for xenial/16.04 in any package) and the 17.04 (and later) packages could just drop the file, because as far as i can see the one in this git is the same as the one libasound2-data distributes

having different packages per release is also how distributions like ubuntu/debian generally handle these issues, so i think it would make sense to use the same mechanisms.