RFR: JDK-8280488: doclint reference checks withstand warning suppression [v2]

[Jonathan Gibbons]

> Please review a small modification to the way that bad references are reported by DocLint.
> 
> A new "mode" is introduced, `strictReferenceChecks`.   
> 
> If the mode is _not_ set, references that explicitly include a module name when that module name is not resolved in the module graph will be reported with a (suppressible) warning instead of an error.  All other issues with references will be reported as errors. This is the mode used by javac.
> 
> If the mode is set, all issues with references will be reported as errors. This is the mode used by javadoc.
> 
> This will need to be documented in the tool guide (man page).

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

  fix typos

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7222/files
  - new: https://git.openjdk.java.net/jdk/pull/7222/files/a529be49..d27de5de

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7222&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7222&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7222.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7222/head:pull/7222

PR: https://git.openjdk.java.net/jdk/pull/7222