Implement C23 memset_explicit (bug 32378)

[Joseph Myers]

On Fri, 26 Sep 2025, Collin Funk wrote:

> Do we want the following workaround from Gnulib so Clang does not
> optimize it away? Copying the snippet from there:

glibc does not support link-time optimization across translation units, 
either within glibc or between glibc and applications; it relies on ABI 
boundaries being present.  So in fact the asm (copied from explicit_bzero) 
isn't really necessary at all at present.

-- 
Joseph S. Myers
josmyers@redhat.com