[PATCH] support: add check_mem_access

[Yury Khrustalev]

Hi,

> > This needs to document the limitations of the implementation: not
> > thread-safe, it changes the SIGSEGV signal handler.
> > 
> > It's possible to avoid both by using vfork to isolate the fault, but
> > it's going to be much slower.
> > 
> > I'd also add the standard license header to the new files

Yes, thank you for the feedback, fixed in v2.

> 
> Yury has asked me for some help to debug the build issue. I think he forgot
> to add this is a WIP change.

Apologies, I should have said it was a WIP patch. Now posted v2 ready
for review:

https://patchwork.sourceware.org/project/glibc/list/?series=51912

Thanks,
Yury