BUG: fix non-swapping strided copies in GetStridedCopySwap

Fixed PyArray_GetStridedCopySwap{Pair,}Fn returns paths that do not swap
the data.
It never triggered because the alignment requirement for complex data
was too low (4-8 bytes) and always fullfiled by the memory allocator.
As this is now fixed it caused failures on sparc with 16 byte long
doubles.