In manifestSp the unwind info was before the relevant instruction, not after.
I added some notes to establish semantics.
Also removes redundant annotation in stg_catch_frame.
For makeFixupBlocks it looks like we were off by wORD_SIZE dflags.
I'm not sure why, but it lines up with manifestSp.
In fact it lines up so well so that I can consolidate the Sp unwind logic
I detected the problems with makeFixupBlocks by running T14779b
after patching D4559.