Re-vendor `perl_pg_driver`

The only reason we need this software definition duplicated locally in our project is so it can have a dependency on `postgresql92`. The upstream version from omnibus-software has a dependency on `postgresql` which causes two copies of PostgreSQL to be built.

/cc @opscode/release-engineers @jamesc @opscode/server-team 

Test CI run: http://wilson.ci.opscode.us/job/chef-server-12-trigger-ad_hoc/238/downstreambuildview/