Restore support for the undocumented <CONFIG>_LOCATION target property
removed by commit v3.0.0-rc1~175^2 (cmTarget: Remove support for
<CONFIG>_LOCATION property, 2013-12-30) as part of the CMP0026 OLD
behavior.
Starting with 3.0 we will use only two components for the feature level,
and policies are only ever introduced with a bump to the feature level
version.
These policies were introduced after 2.8.12 in anticipation of 2.8.13.
However, we've now decided the next release will be 3.0.0, so update the
version of introduction accordingly.