RFR: 8336895: BufferedReader doesn't read full \r\n line ending when it doesn't fit in buffer

[Brian Burkhalter]

Add some verbiage stating that two buffered readers or input streams should not be used to read from the same reader or input stream, respectively.

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Commit messages:
 - 8336895: BufferedReader doesn't read full \r\n line ending when it doesn't fit in buffer

Changes: https://git.openjdk.org/jdk/pull/20320/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20320&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336895
  Stats: 12 lines in 2 files changed: 11 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20320.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20320/head:pull/20320

PR: https://git.openjdk.org/jdk/pull/20320