simdarray: bound alignment to max. 128

simdarray alignment can become really large. GCC starts disliking
alignments above 128 (without SSE at least). So for now, bound it to 128
max.

Signed-off-by: Matthias Kretz <kretz@kde.org>
finitediff: fix IndexesFromZero usage

Signed-off-by: Matthias Kretz <kretz@kde.org>
iif: use const-ref to pass simdarrays efficiently

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