Update to 0.29.3, enable tests
    
    Tests were entirely disabled due to Big Endian failure in one module.
    This enables them back but excludes the failing tests on Big Endian.
    
    Since the tests are quite slow, this also:
    
     * disables CPython regression tests
     * runs the tests in parallel with %{?_smp_mflags} (-j)
    
    However, there are weird test errors on one of the Koji's i686 builders.
    This was reported to upstream: https://github.com/cython/cython/issues/2807
    Until that's sorted out, we skip a test on i686.