RFR: 4847239: (spec) File.createTempFile() should make it clear that it doesn't create the temporary directory [v4]

[Brian Burkhalter]

> Augment the specification of `java.io.File.createTempFile(String,String,File)` to clarify its behavior with respect to the `File` parameter `directory`.

Brian Burkhalter has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains two new commits since the last revision:

 - 4847239: Remove cast, improve exception messages in test
 - 4847239: Modify File.createTempFile verbiage

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4561/files
  - new: https://git.openjdk.java.net/jdk/pull/4561/files/0cd7310d..ce9d4ba6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4561&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4561&range=02-03

  Stats: 6 lines in 2 files changed: 0 ins; 1 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4561.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4561/head:pull/4561

PR: https://git.openjdk.java.net/jdk/pull/4561