RFR: 8296431 - PushbackInputStream should override transferTo [v3]

[Markus KARG]

> This PR implements JDK-8296431

Markus KARG has updated the pull request incrementally with two additional commits since the last revision:

 - Removing synchronization
 - Renamed lock back to closeLock

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10999/files
  - new: https://git.openjdk.org/jdk/pull/10999/files/9d387eaa..f7ee1c7a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10999&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10999&range=01-02

  Stats: 21 lines in 1 file changed: 0 ins; 15 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/10999.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10999/head:pull/10999

PR: https://git.openjdk.org/jdk/pull/10999