[llvm] Add support for fixed-point types (PR #129596)

[Tom Tromey via llvm-commits]

tromey wrote:

> Does llvm-dwarfdump handle them already?

Yes.  With LLVM 19:
```
0x0000117d:   DW_TAG_constant
                DW_AT_GNU_numerator     (0x01)
                DW_AT_GNU_denominator   (0x1e)
```


https://github.com/llvm/llvm-project/pull/129596