Optimize the classpath implementation

  - Avoid repeated conversion between package dotted names ("com.foo")
    and relative paths ("com/foo/") by threading a `PackageName`
    instance through the aggregate classpath lookup which caches
    the path name.
  - Avoid creating result buffers inside of each element of the
    aggregate classpath by introducing a callback based API that
    lets `AggregateClasspath` use a single buffer.

Author: retronym

library/src/scala/collection/mutable/AnyRefMap.scala

@@ -108,8 +108,10 @@ extends AbstractMap[K, V]
     var e = h & mask
     var x = 0
     var g = 0
-    while ({ g = _hashes(e); g != 0}) {
-      if (g == h && { val q = _keys(e); (q eq k) || ((q ne null) && (q equals k)) }) return e
+    val hashes = _hashes
+    val keys = _keys
+    while ({ g = hashes(e); g != 0}) {
+      if (g == h && { val q = keys(e); (q eq k) || ((q ne null) && (q equals k)) }) return e
       x += 1
       e = (e + 2*(x+1)*x - 3) & mask
     }