RFR: JDK-8250766: javadoc adds redundant spaces when @see program element is wrapped [v5]

[Hannes Wallnöfer]

> This changes reference parsing in `DocCommentParser` to normalize whitespace in signatures to a large extent. In particular, multiple whitespace characters are coalesced into a single space character, and whitespace after opening parentheses and angle brackets are suppressed.

Hannes Wallnöfer has updated the pull request incrementally with one additional commit since the last revision:

  JDK-8250766: Add missing null check and update copyright year

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3754/files
  - new: https://git.openjdk.java.net/jdk/pull/3754/files/1a1ee57d..13589ffc

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3754&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3754&range=03-04

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3754.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3754/head:pull/3754

PR: https://git.openjdk.java.net/jdk/pull/3754