libapparmor: build perl bindings

There are still a few utils which use Perl, though most have been ported to
Python. Note that SWIG v2 is required to avoid the `error: 'bool' undeclared`
build failure with Perl >=5.16 [1].

[1]: https://github.com/swig/swig/commit/4305a3cef9b210541c3b88ab2fd03d787c3bca66