RFR: 8296431 - PushbackInputStream should override transferTo [v5]

[Markus KARG]

> This PR implements JDK-8296431

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

  Removed unused imports

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10999/files
  - new: https://git.openjdk.org/jdk/pull/10999/files/b6f4d8cb..baaf1c6a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10999&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10999&range=03-04

  Stats: 16 lines in 1 file changed: 0 ins; 16 del; 0 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