RFR: 8296420: javac has long lines in its command-line help [v3]

[Archie L. Cobbs]

> The issue states that the output of `javac --help` and `javac --help-extra` should not overflow 80 columns.
> 
> This patch updates `javac.properties` to add newlines, etc. to address this issue, and adds a regression test.

Archie L. Cobbs has updated the pull request incrementally with two additional commits since the last revision:

 - Show all offending lines in exception message, not just the first.
 - Relocate help text split point to just after a period.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13329/files
  - new: https://git.openjdk.org/jdk/pull/13329/files/cfc2c3da..2137122d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13329&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13329&range=01-02

  Stats: 8 lines in 2 files changed: 1 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/13329.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13329/head:pull/13329

PR: https://git.openjdk.org/jdk/pull/13329