RFR: JDK-8290126: Add a check in JavadocTester for "javadoc should not crash" [v7]

[Jonathan Gibbons]

> Please review a simple update to `JavadocTester` to provide a default-on check that no stack traces were written to the STDERR stream.
> 
> There are also some minor cleanup edits suggested by the IDE.

Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  update copyright

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9458/files
  - new: https://git.openjdk.org/jdk/pull/9458/files/24be548e..a3884dd4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9458&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9458&range=05-06

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9458.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9458/head:pull/9458

PR: https://git.openjdk.org/jdk/pull/9458