Fix simdarray unit test segfaults
Fix simdarray unit test segfaults

The test was using Vc::Memory with non-power-of-two SimdArray. This made
most of the vector accesses reference unaligned addresses and thus crash
the test.
Use alignas with C-array to get the memory we need.

Refs: gh-50
Signed-off-by: Matthias Kretz <372ea4eca737a13cd010ee806d4ce7b98ee71550@kde.org>

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