[lworld] RFR: Prototype inline cursors for List

[Roger Riggs]

Implementation of Cursors and jmh tests comparing
typical List traversal via direct index, iterator,
inline cursor, and an iterator implemented on top of cursor.

Sample results:

                                   (size)  Mode  Cnt       Score       Error  Units
XArrayListCursorTest.getViaArray            100000  avgt    5  507793.484  7086.038  ns/op
XArrayListCursorTest.getViaCursorForLoop    100000  avgt    5  656461.958  52488.547  ns/op
XArrayListCursorTest.getViaCursorWhileLoop  100000  avgt    5  641963.323  32219.409  ns/op
XArrayListCursorTest.getViaIterator         100000  avgt    5  558863.817  23539.256  ns/op
XArrayListCursorTest.getViaIteratorCurs     100000  avgt    5  733161.466  33721.881  ns/op

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Commit messages:
 - Prototype inline cursors for List

Changes: https://git.openjdk.java.net/valhalla/pull/5/files
 Webrev: https://webrevs.openjdk.java.net/valhalla/5/webrev.00
  Stats: 2139 lines in 3 files changed: 2139 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/5.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/5/head:pull/5

PR: https://git.openjdk.java.net/valhalla/pull/5