RFR: 8313368: (fc) FileChannel.size returns 0 on block special files [v2]

[Brian Burkhalter]

> Reinstate header files so that `BLKGETSIZE64` is defined on Linux.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8313368: Change conditional compilation check; modify existing test to be manual

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15092/files
  - new: https://git.openjdk.org/jdk/pull/15092/files/f2ec65c4..52c2f41f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15092&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15092&range=00-01

  Stats: 6 lines in 2 files changed: 1 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/15092.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15092/head:pull/15092

PR: https://git.openjdk.org/jdk/pull/15092