remove cast::unsafe_copy

This is the same functionality as `ptr::read_ptr`.

src/libstd/cast.rs

@@ -25,14 +25,6 @@ pub unsafe fn transmute_copy<T, U>(src: &T) -> U {
     dest
 }
 
-/**
- * Forces a copy of a value, even if that value is considered noncopyable.
- */
-#[inline]
-pub unsafe fn unsafe_copy<T>(thing: &T) -> T {
-    transmute_copy(thing)
-}
-
 /**
  * Move a thing into the void
  *