Proposed new feature or change:

PowerPC is transitioning from AIX longdouble to IEEE longdouble. Fortunately, NumPy's check for longdouble format works through this transition and does not break any tests.

However, test_ppc64_ibm_double_double128 is keyed only on ppc64, and has started failing when the system uses IEEE long doubles (since they're 'normal' and don't have the semantics that this test is checking.) I don't know how to determine (at runtime) what long double format NumPy determined (at build time), but if possible, this test should check that and only run for AIX long doubles.