All of the other dead keys are defined in the 0xfe00 block.  0xfe67 thru 0xfe6f are available at the end of the current dead key block.

I’d suggest using that block for these symbols.

If there is no objection I can push it using them.

(Unless you want this one, Daniel.)

Err, forgot to say that the reason for the suggestion is that the unicode combining characters have different semantics than dead keys and the two should be kept as separate entities.

I pushed this with keysyms in the 0xfe60 range.

Commit:  44e24a27bca023cf7b799f191fe6d52e12efbe5f

I'll also push an addition to the Compose.pre in libX11 to use them
for the precomposed latin characters.