RFR: 8294696 - BufferedInputStream.transferTo should drain buffer when mark set [v4]

[Markus KARG]

> This PR implements JDK-8294696.

Markus KARG has updated the pull request incrementally with one additional commit since the last revision:

  Prevent leaking and poisoning

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10525/files
  - new: https://git.openjdk.org/jdk/pull/10525/files/edd9da50..7350a533

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10525&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10525&range=02-03

  Stats: 16 lines in 1 file changed: 12 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10525.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10525/head:pull/10525

PR: https://git.openjdk.org/jdk/pull/10525