Add a new ATF test, sigs_test, containing everything required to start
defining test cases for dns__zone_updatesigs(). The framework is
written in a way which ensures that changes to zone database applied by
any dns__zone_updatesigs() invocation are preserved between subsequent
checks.
version 0.12) for development of future unit tests.
Use configure --with-atf to build ATF internally
or configure --with-atf=prefix to use an external
copy. [RT #23209]