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.
Merge pull request #641 from opscode/schisamo/revendor-perl_pg_driver

Re-vendor `perl_pg_driver`