RFR: 8287333: Clean up ParamTaglet and ThrowsTaglet [v3]

[Pavel Rappo]

> A cleanup to facilitate fixing bugs like JDK-6509045: `{@inheritDoc}` only copies one instance of the specified exception.

Pavel Rappo has updated the pull request incrementally with three additional commits since the last revision:

 - Remove upper-bounded wildcard
   
   This change simplifies code without any disadvantages:
   
     * Those `List<? extends XTree>` are read-only
     * An argument of the `List<XTree>` type can still be passed to a `List<? extends XTree>` parameter
 - Simplify inheritThrowsDocumentation
 - Reuse more specific variable

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8886/files
  - new: https://git.openjdk.java.net/jdk/pull/8886/files/7f1d9324..fbd9d76a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8886&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8886&range=01-02

  Stats: 48 lines in 3 files changed: 10 ins; 3 del; 35 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8886.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8886/head:pull/8886

PR: https://git.openjdk.java.net/jdk/pull/8886