RFR: 8263333: Improve links from core reflection to JLS and JVMS

[Joe Darcy]

The javadoc of various methods in core reflection would be improved by links into the JLS.

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Commit messages:
 - 8263333: Improve links from core reflection to JLS and JVMS

Changes: https://git.openjdk.java.net/jdk/pull/2906/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2906&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263333
  Stats: 21 lines in 5 files changed: 20 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2906.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2906/head:pull/2906

PR: https://git.openjdk.java.net/jdk/pull/2906