simdize: has_tuple_interface checks for usable get<N>
simdize: has_tuple_interface checks for usable get<N>

extend has_tuple_interface to check for get<N> has well. Also added a
constexpr function to make it easier to use

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

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