Add access to stdin, stdout, stderr names somehow

[tbu-]

Earlier request: #7.
Implementation attempt: #1073.

One problem with this is that these names are apparently not symbols but only macros on some operating systems. (The C standard doesn't require these to be symbols.)

[thewh1teagle]

I also need to access stdout handle. Currently I'm using https://github.com/crlf0710/libc-stdhandle instead but I prefer to use it from this crate instead.
Does it possible already?

[tbu-]

@tgross35 Definitely not E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. , it needs a decision on how to export identifiers only exposed as macros in C. errno seems to have gotten special treatment because it has libc::__errno_location, but an earlier attempt to copy that to stdin, stdout and stderr was rejected, see #1073 (comment) where it says we need an RFC to support stdin etc.