Add pairwise testing

Add pairwise testing

Pairwise testing is a test case generation technique based on the
observation that most faults are caused by interactions of at most two
factors.  For BIND, its configure options can be thought of as such
factors.

Process BIND configure options into a model that is subsequently
processed by the PICT tool in order to find an effective test vector.
That test vector is then used for configuring and building BIND using
various combinations of configure options.

(cherry picked from commit 420986bf187ed2a33321d5af362732184426f439)