all: VAES instructions (#358)

Adds "Vector Advanced Encryption Standard" instruction set.

These are added via the `opcodesextra` mechanism #345, since they're missing
from the opcodes database.

Contributed by @vsivsi. Extracted from #349 with minor tweaks.

Co-authored-by: Vaughn Iverson <vsivsi@yahoo.com>

internal/opcodesextra/instructions.go

@@ -7,6 +7,7 @@ import "github.com/mmcloughlin/avo/internal/inst"
 var sets = [][]*inst.Instruction{
 	movlqzx,
 	gfni,
+	vaes,
 }
 
 // Instructions returns a list of extras to add to the instructions database.