S RFR: 8012294: remove generic default handling

[Karen Kinnear]

Please review:

webrev:  http://cr.openjdk.java.net/~acorn/8012294/webrev/
http://bugs.sun.com/view_bug.do?bug_id=8012294

This is a cleanup bug - fix 8013635 removed generic signature support from the vm
default method handling, but as a temporary fallback, put this under the develop flag
ParseGenericDefaults. This has been shaken out sufficiently that the old code under
that flag can now be removed, including ParseGenericDefaults and ParseAllGenericSignatures,
both of which were temporary develop flags for early lambda default method handling.

tests:
java -XX:+ParseGenericDefaults -XX:+CompileTheWorld -Xbootclasspath/p:<mypath>db.jar - fails before change
java -XX:+ParseGenericDefaults - won't start VM after change
java -XX:+ParseAllGenericSignatures - won't start VM after change
jprt
defmeth tests (no new failures)
vm.quick.testlist in progress

thanks,
Karen