RFR: 8287333: Clean up ParamTaglet and ThrowsTaglet [v4]

[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 with a new target base due to a merge or a rebase. The pull request now contains 33 commits:

 - Merge branch 'master' into 8287333
   
   This resolves a conflict in ParamTaglet.
 - Clean up if-branch
 - 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
 - Merge branch 'master' into 8287333
 - Incremental update
   
   - Renames local variables and method parameters
   - Improves comments
   - Removes debug leftovers
 - Update top-level doc comment
 - Trivially re-order assignments
   
   ...for re-use
 - Reformat for clarity
   
   Now it's very clear that the "Throws:" section consists of three types of exceptions:
   
     1. documented
     2. inherited
     3. undocumented
 - ... and 23 more: https://git.openjdk.java.net/jdk/compare/ebc012ec...6bbe871b

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Changes: https://git.openjdk.java.net/jdk/pull/8886/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8886&range=03
  Stats: 418 lines in 4 files changed: 113 ins; 151 del; 154 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