Distribute debug symbols for release builds

We should distribute debug symbols on all the linux platforms for our release builds.

There are two options here:

1. Include debug symbols in the distributed libraries, relying on cabal and other build tools calling strip (as per the users configuration, but cabal does call strip by default) to ensure that most binaries that users compile are unaffected unless they opt in to the symbols.
2. Include debug symbols separately from the library object files.

The only drawback is the increased size of the release archives, but this could be avoided if we follow option 2. and distribute them as part of a companion tarball.