RFR: 7036144: GZIPInputStream readTrailer uses faulty available() test for end-of-stream [v7]

[Archie Cobbs]

> `GZIPInputStream`, when looking for a concatenated stream, relies on what the underlying `InputStream` says is how many bytes are `available()`. But this is inappropriate because `InputStream.available()` is just an estimate and is allowed (for example) to always return zero.
> 
> The fix is to ignore what's `available()` and just proceed and see what happens. If fewer bytes are available than required, the attempt to extend to another stream is canceled just as it was before, e.g., when the next stream header couldn't be read.

Archie Cobbs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Document the handling of concatenated streams.
 - Merge branch 'master' into JDK-7036144
 - Merge branch 'master' into JDK-7036144
 - Merge branch 'master' into JDK-7036144
 - Address third round of review comments.
 - Address second round of review comments.
 - Address review comments.
 - Fix bug in GZIPInputStream when underlying available() returns short.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17113/files
  - new: https://git.openjdk.org/jdk/pull/17113/files/f4178acc..d557d8c6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17113&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17113&range=05-06

  Stats: 123995 lines in 2894 files changed: 27722 ins; 83983 del; 12290 mod
  Patch: https://git.openjdk.org/jdk/pull/17113.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17113/head:pull/17113

PR: https://git.openjdk.org/jdk/pull/17113