simd_cast: conversions from SSE::int_v to AVX
simd_cast: conversions from SSE::int_v to AVX

The SSE::int_v conversions to AVX vectors are most important because the
IndexType member type uses SSE::int_v. This should make it work.

refs #598

Signed-off-by: Matthias Kretz <372ea4eca737a13cd010ee806d4ce7b98ee71550@kde.org>

chr-engwer/Vc,chr-engwer/Vc,VcDevel/Vc,VcDevel/Vc,VcDevel/Vc,chr-engwer/Vc,VcDevel/Vc