Fix some issues reported by lintian

Fix some issues reported by lintian

• Bump debhelper from old 9 to 12.
• Set debhelper-compat version in Build-Depends.
• debian/copyright: use spaces rather than tabs to start continuation lines.
• Set upstream metadata fields: Repository, Repository-Browse.
• Drop unnecessary dependency on dh-autoreconf.
• Update standards version to 4.4.1, no changes needed.

This merge proposal was created automatically by the Janitor bot (https://janitor.debian.net/lintian-fixes).

You can follow up to this merge proposal as you normally would.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/pcaudiolib/0ce34061-f3ab-4ed2-b65b-081871b28040.