Update PE mock configs to set the %vendor macro so that the Vendor tag will be populated in built rpms.
Merge pull request #33 from haus/update_PE_mocks_with_vendor

Update PE mock configs to set the %vendor macro so that the Vendor tag w...
Add mock definitions for EL4

This commit adds support for mocking on EL4.

In it's current incarnation, there are a few oddities.
  * EL 4 uses vault.centos since yo isn't setup with a proper RHEL
  * I've created a legacy_mock defined type because it's a very
    different template.
  * This will only work at PL, since it's pointed to neptune.