refactor libcollections as part of collection reform

* Moves multi-collection files into their own directory, and splits them into seperate files
* Changes exports so that each collection has its own module
* Adds underscores to public modules and filenames to match standard naming conventions

(that is, treemap::{TreeMap, TreeSet} => tree_map::TreeMap, tree_set::TreeSet)

* Renames PriorityQueue to BinaryHeap
* Renames SmallIntMap to VecMap
* Miscellanious fallout fixes

[breaking-change]

src/test/bench/core-set.rs

@@ -14,7 +14,7 @@ extern crate collections;
 extern crate rand;
 extern crate time;
 
-use std::collections::bitv::BitvSet;
+use std::collections::BitvSet;
 use std::collections::TreeSet;
 use std::hash::Hash;
 use std::collections::HashSet;

src/test/bench/std-smallintmap.rs

@@ -13,17 +13,17 @@
 extern crate collections;
 extern crate time;
 
-use std::collections::SmallIntMap;
+use std::collections::VecMap;
 use std::os;
 use std::uint;
 
-fn append_sequential(min: uint, max: uint, map: &mut SmallIntMap<uint>) {
+fn append_sequential(min: uint, max: uint, map: &mut VecMap<uint>) {
     for i in range(min, max) {
         map.insert(i, i + 22u);
     }
 }
 
-fn check_sequential(min: uint, max: uint, map: &SmallIntMap<uint>) {
+fn check_sequential(min: uint, max: uint, map: &VecMap<uint>) {
     for i in range(min, max) {
         assert_eq!(map[i], i + 22u);
     }
@@ -45,7 +45,7 @@ fn main() {
     let mut appendf = 0.0;
 
     for _ in range(0u, rep) {
-        let mut map = SmallIntMap::new();
+        let mut map = VecMap::new();
         let start = time::precise_time_s();
         append_sequential(0u, max, &mut map);
         let mid = time::precise_time_s();

src/test/run-fail/hashmap-capacity-overflow.rs

@@ -10,7 +10,7 @@
 
 // error-pattern:capacity overflow
 
-use std::collections::hashmap::HashMap;
+use std::collections::hash_map::HashMap;
 use std::uint;
 use std::mem::size_of;
 

src/test/run-pass/auto-encode.rs

@@ -17,7 +17,7 @@ extern crate time;
 // These tests used to be separate files, but I wanted to refactor all
 // the common code.
 
-use std::hashmap::{HashMap, HashSet};
+use std::collections::{HashMap, HashSet};
 
 use rbml::reader as EBReader;
 use rbml::writer as EBWriter;

src/test/run-pass/while-let.rs

@@ -10,10 +10,10 @@
 
 #![feature(while_let)]
 
-use std::collections::PriorityQueue;
+use std::collections::BinaryHeap;
 
-fn make_pq() -> PriorityQueue<int> {
-    PriorityQueue::from_vec(vec![1i,2,3])
+fn make_pq() -> BinaryHeap<int> {
+    BinaryHeap::from_vec(vec![1i,2,3])
 }
 
 pub fn main() {