[Bug c/92720] cc1 accepts #include /dev/stdin inline

[dclarke at blastwave dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92720

--- Comment #5 from Dennis Clarke <dclarke at blastwave dot org> ---

Glad someone looked at this. I was going to try again with LLVM/Clang
and then a few other places on a few other architectures. Why bother? 

However if this is "implementation defined" then we should see a
paragraph somewhere in a standards doc regarding this. Somewhere.