arm64asm rejects three exception-space words the toolchain's corpus
assembles: the hypervisor call HVC, the secure monitor call SMC and
the speculation barrier SB. The supplementary naming table reads
the raw word in the error branch and renders the corpus spellings;
the corpus rows are pinned in the parity fixture and the boundary
test holds the unallocated neighbours on the placeholder.
Assisted-by: GLM 5.3
