std::vec: Remove the function same_length

The basic construct x.len() == y.len() is just as simple.

This function used to be a precondition (not sure about the
terminology), so it had to be a function. This is not relevant any more.

src/libstd/vec.rs

@@ -123,11 +123,6 @@ use unstable::raw::{Box, Repr, Slice, Vec};
 use vec;
 use util;
 
-/// Returns true if two vectors have the same length
-pub fn same_length<T, U>(xs: &[T], ys: &[U]) -> bool {
-    xs.len() == ys.len()
-}
-
 /**
  * Creates and initializes an owned vector.
  *