[libcxxabi] [llvm] [demangler] Enhance demangling in llvm-cxxfilt for fixed-point types. (PR #114257)

[via llvm-commits]

c8ef wrote:

```
UNRESOLVED: lldb-api :: tools/lldb-dap/evaluate/TestDAP_evaluate.py (2635 of 2635)
```

Seems irrelevant.

https://github.com/llvm/llvm-project/pull/114257