collections: Move push/pop to MutableSeq

Implement for Vec, DList, RingBuf. Add MutableSeq to the prelude.

Since the collections traits are in the prelude most consumers of
these methods will continue to work without change.

[breaking-change]

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index e14092bc8dc..125c3fdf5d9 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -288,4 +288,6 @@ mod std {
     #[cfg(test)] pub use os = realstd::os;
     // The test runner requires std::slice::Vector, so re-export std::slice just for it.
     #[cfg(test)] pub use slice;
+
+    pub use collections; // vec!() uses MutableSeq
 }