x86emul: support AVX512F scatter insns

x86emul: support AVX512F scatter insns

This completes support of AVX512F in the insn emulator.

Note that in the test harness there's a little bit of trickery needed to
get around the not fully consistent naming of AVX512VL gather and
scatter compiler built-ins. To suppress expansion of the "di" and "si"
tokens they get constructed by token concatenation in BS(), which is
different from BG().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>