RFR: 8268148: unchecked warnings handle ? and ? extends Object differently [v2]

[Vicente Romero]

> Please review this PR. Currently javac handles differently `?` and `? extends Object` when reporting unchecked warnings when according to the spec they should be handled the same way. This PR is fixing this.
> 
> TIA

Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:

  addressing review comments

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5224/files
  - new: https://git.openjdk.java.net/jdk/pull/5224/files/cfbede77..511890b0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5224&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5224&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5224.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5224/head:pull/5224

PR: https://git.openjdk.java.net/jdk/pull/5224