RFR: 8266822: Rename MetaspaceShared::is_old_class to has_old_class_version [v2]

[Calvin Cheung]

> Please review this simple patch for renaming the function from `MetaspaceShared::is_old_class` to `MetaspaceShared::has_old_class_version`. Also added some comment to the function.
> 
> Tests:
> - [x] tier1, 2

Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:

  update comment

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3983/files
  - new: https://git.openjdk.java.net/jdk/pull/3983/files/3cb3825d..6ae1e11c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3983&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3983&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3983.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3983/head:pull/3983

PR: https://git.openjdk.java.net/jdk/pull/3983