Adds support for building facter on RHEL7 via spec.
Add initial support for building in a RHEL 7 mock

RHEL7 support is being added for x86_64 only; we'll fix/expand
this if upstream releases a 32-bit version of RHEL7.
Merge pull request #616 from mckern/add-el7-to-stable

Apply the RHEL7 work and merge it into stable
(packaging) Update FACTERVERSION to 1.7.5-rc2
Merge tag '1.7.5-rc2'

1.7.5-rc2

* tag '1.7.5-rc2':
  (packaging) Update FACTERVERSION to 1.7.5-rc2
  Add initial support for building in a RHEL 7 mock
  Adds support for building facter on RHEL7 via spec.