[lworld] RFR: allow inline classes to have abstract supers

[Harold Seigel]

Plesae review this change to allow inline classes to have super classes that are abstract classes.  This fix does not
test that the abstract classes are 'special'.  That will be done in a future release.

Also, fix verification issue with assigning an inline type to an object of one of its super classes.

Tests will be added once javac support for inline types having abstract classes is merged in.

Thanks, Harold

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Commit messages:
 - allow inline classes to have abstract supers

Changes: https://git.openjdk.java.net/valhalla/pull/24/files
 Webrev: https://webrevs.openjdk.java.net/valhalla/24/webrev.00
  Stats: 21 lines in 3 files changed: 14 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/24.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/24/head:pull/24

PR: https://git.openjdk.java.net/valhalla/pull/24