RFR: 8288080: (fc) FileChannel::map for MemorySegments should state it always throws UOE [v2]

[Brian Burkhalter]

> Add an `@implSpec` annotation to the `java.nio.channels.FileChannel::map` method for mapped memory segments indicating that it always throws an `UnsupportedOperationException`.

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

  8288080: Simplify @implSpec verbiage

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9095/files
  - new: https://git.openjdk.org/jdk/pull/9095/files/2b93620e..e7119ce2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=9095&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=9095&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9095.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9095/head:pull/9095

PR: https://git.openjdk.org/jdk/pull/9095