[code-reflection] RFR: Address var name

[Mourad Abbay]

Address var name

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

Commit messages:
 - Add method CoreOp.VarOp.isUnnamedVariable
 - Update javadoc of CoreOp.var factory methods

Changes: https://git.openjdk.org/babylon/pull/235/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=235&range=00
  Stats: 8 lines in 1 file changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/babylon/pull/235.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/235/head:pull/235

PR: https://git.openjdk.org/babylon/pull/235