[fpc-pascal] avx2 32-byte alignment

[Marco van de Voort]

I'm preparing a DLL with AVX2 routines in FPC, since Delphi doesn't seem to
have AVX2 support.

I wonder if it is possible to align constants used for shuffling
(array[0..31] of byte typically) on 32-byte borders, so that I can use them
directly in the code.

Till now I preloaded the constants using unaligned instructions before the
loop, but I'm running out of registers in the current iteration.

(win64/x86_64 only btw, but I assume the possible data alignments aren't target
dependent)