If qtox is installed in /usr/local prefix (for example), launching qTox
fails because loading libraries from @{qtox_prefix} directory was not
allowed.
Add rule to allow loading libraries from @{qtox_prefix}/lib directory.
Copy 2.13.2 profile into 2.12.1 place to be the starting point for
modifying (backporting) AppArmor profile for version 2.12.1 (on Ubuntu
18.04, Debian Stretch, etc).
At this point 2.12.1 profile does not work, as AppArmor v2.12.1 does not
have needed abstractions and policy language features (such as `include
if exists`). Followup commits will fix these issues.