RFR: 8266571: Sequenced Collections [v6]

[Stuart Marks]

> PR for Sequenced Collections implementation.

Stuart Marks has updated the pull request incrementally with four additional commits since the last revision:

 - Clarify LHM and LHS specs regarding semantics of reverse-ordered views.
 - Remove special-cases for reversed LHM and LHS putAll and add.
 - Minor cleanups including formatting, naming, comments, modifiers.
 - Add @implSpec to default methods where it was missing.
   Add removeFirst/removeLast default methods to NavigableSet.
   Add throwing putFirst/putLast to TreeMap & ConcurrentSkipListMap
   Add throwing addFirst/addLast to TreeSet & ConcurrentSkipListSet
   Clarify access order specification for LinkedHashMap.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/7387/files
  - new: https://git.openjdk.org/jdk/pull/7387/files/1332c3e2..0b8e6dfe

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=7387&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=7387&range=04-05

  Stats: 351 lines in 18 files changed: 290 ins; 13 del; 48 mod
  Patch: https://git.openjdk.org/jdk/pull/7387.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/7387/head:pull/7387

PR: https://git.openjdk.org/jdk/pull/7387