the behavior of a defined word instruction in the suffix.
```
+thus, we have:
+
+| 0-5 | 6 | 7 | 8-31 | Description |
+|------|---|---|------|---------------------------|
+|EXT001| 0 | 0 | nnnn | new, |
+|EXT001| 1 | 0 | nnnn | suffix=defined-word |
+|EXT001| 0 | 1 | nnnn | new, |
+|EXT001| 1 | 1 | nnnn | suffix=defined-word |
+
+
this "doubling" is already public and part of EXT001, the idea
here is to mirror that (bit 6), but unlike EXT001, use bit 7
to mark whether the instruction is SVP64-vector or SVP64-single.