RFR: 8306980: Generated docs should contain correct GPLv2 Legal Documents [v4]

[KIRIYAMA Takuya]

> I modified the location from which javadoc copies some legal files to the generated documentation.  If --legal-notices　option is set to default or nothing is specified,, GPLv2 Legal Documents are copied from legal/java.base/ directory, such as LICENSE, ADDITIONAL_LICENSE_INFO and ASSEMBLY_EXCEPTION.
> 
> Would you please review this fix?

KIRIYAMA Takuya has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge remote-tracking branch 'origin' into 8306980
 - 8306980: Generated docs should contain correct GPLv2 Legal Documents
 - 8306980: Generated docs should contain correct GPLv2 Legal Documents
 - 8306980: Generated docs should contain correct GPLv2 Legal Documents

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13686/files
  - new: https://git.openjdk.org/jdk/pull/13686/files/ff2bf451..f02668f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13686&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13686&range=02-03

  Stats: 274603 lines in 4241 files changed: 206005 ins; 37252 del; 31346 mod
  Patch: https://git.openjdk.org/jdk/pull/13686.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13686/head:pull/13686

PR: https://git.openjdk.org/jdk/pull/13686