Simple macro that works just like C's ##

Example

```rust use clikeconcat::concat;

[derive(Debug, Eq, PartialEq)]

struct FuzzBuzz;

fn main() { asserteq!(concat!(0 ## x ## 42), 0x42); asserteq!(concat!(Fuzz ## Buzz), FuzzBuzz); // Sadly, but following code works // as stringify! will expand to "concat! (Fuzz # # Buzz)", // not to "FuzzBuzz" assert_eq!(stringify!(concat!(Fuzz ## Buzz)), "concat! (Fuzz # # Buzz)"); }

```