auto merge of #19955 : Gankro/rust/kill-all-code, r=aturon

EnumSet lives on in libcollections so that librustc can still use it. This adds a direct dependency on libcollections to librustc and libserialize.

Should not be merged until rust-lang/rfcs#509 is accepted.

All of these collections have already been moved to collect-rs where they will ideally be maintained and experimented with, or will be replaced by something better: https://github.com/Gankro/collect-rs/

[breaking-change]

r? @aturon @alexcrichton

src/libcollections/lib.rs

@@ -46,10 +46,6 @@ pub use dlist::DList;
 pub use enum_set::EnumSet;
 pub use ring_buf::RingBuf;
 pub use string::String;
-pub use tree_map::TreeMap;
-pub use tree_set::TreeSet;
-pub use trie_map::TrieMap;
-pub use trie_set::TrieSet;
 pub use vec::Vec;
 pub use vec_map::VecMap;
 
@@ -61,8 +57,6 @@ mod btree;
 pub mod dlist;
 pub mod enum_set;
 pub mod ring_buf;
-mod tree;
-mod trie;
 pub mod slice;
 pub mod str;
 pub mod string;
@@ -77,22 +71,6 @@ pub mod bitv_set {
     pub use bit::{BitvSet, BitPositions, TwoBitPositions};
 }
 
-pub mod tree_map {
-    pub use tree::map::*;
-}
-
-pub mod tree_set {
-    pub use tree::set::*;
-}
-
-pub mod trie_map {
-    pub use trie::map::*;
-}
-
-pub mod trie_set {
-    pub use trie::set::*;
-}
-
 pub mod btree_map {
     pub use btree::map::*;
 }