[Piglit] Set default platform in pigilt.conf

[Dylan Baker]

This series adds support for setting the default platform used by waffle
in piglit.conf. It seems like a rather long series, but the majority of
the series is either refactoring code to allow changes, or working on
the unit tests, (In fact, 11 of the 18 patches in this series much with
unit tests).

Patches 2-7: Fix bugs in both the unit tests for loading piglit.conf,
             and the actual code for loading piglit files, these patches
			 are needed since without them patch 18 will exercise bugs
			 that they fix them.
Patches 8-15: Make additional cleanups to the tests for piglit.conf,
Patches 16-17: Do the legwork of the series, 16 makes the majority of
               the changes necessary to use the config file to set
			   default values, while patch 18 actually implements the
			   first user of this feature.

This is available at my github:
https://github.com/dcbaker/piglit submit/conf-defaults

Jordan -- This is what you wanted, correct?