Compiler incorrectly whines about redefinition of procs that take different instances.

``` nimrod
type TType[T; A] = array[A, T]

proc foo[T](p: TType[T, range[0..1]]) =
  echo "foo"
proc foo[T](p: TType[T, range[0..2]]) =
  echo "bar"
```

As a human can see, the two foo's take different parameters. But the lovely little git known as the compiler thinks they are identical, and spits out:

```
poop.nim(5, 0) Error: redefinition of 'foo'
```

So let's fix it.
