Catch reverse ranges in for loops

[Manishearth]

fn main() {
   for i in (10..0) {
    println!("{}", i);
   } 
}

should be

fn main() {
   for i in (0..10).rev() {
    println!("{}", i);
   } 
}

rust-lang/rust#26975

Might be a bit tricky to handle due to desugaring.

[llogiq]

This is a duplicate of #96.