[PATCH v2 0/1] MR7231: rpcrt4, winedbg, winevulkan: Various small fixes for Clang 20 + -Werror.

[William Horvath (＠whrvth)]

I don't think these are serious problems, but Clang 20's defaults (from llvm-mingw nightly) were resulting in build failures with `--enable-werror` due to `-Wtautological-compare` and `-Wunused-function`. I hope that the buffer wrap checking is somewhat idiomatic/standard.

If necessary, I can split off the winevulkan change, but it seems minor enough to be grouped in this MR.

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  v2: rpcrt4: Pointer arithmetic fixes (-Wtautological-compare).
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/7231