RFR: 8293502: (fc) FileChannel::transfer methods fail to copy /proc files on Linux [v2]

[Brian Burkhalter]

> Files in `/proc` advertise a size of zero for which direct and mapped transfers do not work. For this case, fall back to arbitrary channel transfer.

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

  8293502: Use /proc/cpuinfo instead of /proc/mounts and other cleanup

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10267/files
  - new: https://git.openjdk.org/jdk/pull/10267/files/1b009421..95901194

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10267&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10267&range=00-01

  Stats: 11 lines in 2 files changed: 3 ins; 2 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/10267.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10267/head:pull/10267

PR: https://git.openjdk.org/jdk/pull/10267