Dealing with CRLF in Rust printing

["Ayush Singh" <ayushdevel1325@gmail.com>]

Hello everyone, I have been somewhat successful in implementing Rust
stdio for UEFI.

This means it is now possible to do things like this:
```rust
let s = 10;
println!("ConOut: {}", s);
eprintl!("StdErr: {}", s);
```

However, Rust uses LF on all platforms currently, which means that the
`println!`, `eprintln!` and other macros only output LF at the end.

After discussion in zulipchat [1], it seems that rather than changing
the macro, it would be better to change what is printed as output.
This means changing: `\n` to `\r\n`, when we go for printing to
screen.

Note: This means that the LF will be changed to CRLF only when using
stdio and not when writing to say an external file.

Firstly, I wanted to ask other people's opinions about doing this.
Secondly, I wanted to ask if `\r\r\n` is the same as `\r\n` or if the
extra CR should be trimmed.

Ayush Singh

[1]: https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/.60println!.60.20for.20CRLF.20console