Prelude: rename and consolidate extension traits

This commit renames a number of extension traits for slices and string
slices, now that they have been refactored for DST. In many cases,
multiple extension traits could now be consolidated. Further
consolidation will be possible with generalized where clauses.

The renamings are consistent with the [new `-Prelude`
suffix](rust-lang/rfcs#344). There are probably
a few more candidates for being renamed this way, but that is left for
API stabilization of the relevant modules.

Because this renames traits, it is a:

[breaking-change]

However, I do not expect any code that currently uses the standard
library to actually break.

Closes #17917

maybe_owned_vec.rs

@@ -12,7 +12,7 @@ use std::default::Default;
 use std::fmt;
 use std::iter::FromIterator;
 use std::path::BytesContainer;
-use std::slice;
+use std::slice::{mod, Permutations};
 
 // Note 1: It is not clear whether the flexibility of providing both
 // the `Growable` and `FixedLen` variants is sufficiently useful.
@@ -137,11 +137,19 @@ impl<'a,T:fmt::Show> fmt::Show for MaybeOwnedVector<'a,T> {
     }
 }
 
-impl<'a,T:Clone> CloneableVector<T> for MaybeOwnedVector<'a,T> {
+impl<'a,T:Clone> CloneSliceAllocPrelude<T> for MaybeOwnedVector<'a,T> {
     /// Returns a copy of `self`.
     fn to_vec(&self) -> Vec<T> {
         self.as_slice().to_vec()
     }
+
+    fn partitioned(&self, f: |&T| -> bool) -> (Vec<T>, Vec<T>) {
+        self.as_slice().partitioned(f)
+    }
+
+    fn permutations(&self) -> Permutations<T> {
+        self.as_slice().permutations()
+    }
 }
 
 impl<'a, T: Clone> Clone for MaybeOwnedVector<'a, T> {
@@ -153,7 +161,6 @@ impl<'a, T: Clone> Clone for MaybeOwnedVector<'a, T> {
     }
 }
 
-
 impl<'a, T> Default for MaybeOwnedVector<'a, T> {
     fn default() -> MaybeOwnedVector<'a, T> {
         Growable(Vec::new())