RFR 8186092: Unnecessary loader constraints produced when there are multiple defaults

[harold seigel]

Hi,

Please review this JDK-10 change to fix JDK-8186092.  The change 
prevents the checking of loader constraints during vtable and itable 
creation if the selected method is an overpass method. Overpass methods 
are created by the JVM to throw exceptions and so should not be 
subjected to loader constraint checking.

Additionally, this change improves the LinkageError exception error text 
when a loader constraint violation occurs during vtable and itable 
creation.

The fix includes four new tests, one test each to check that loader 
constraint checking is not done for overpass methods during vtable and 
itable creation, and one test each to test the new vtable and itable 
loader constraint error messages.

Open webrev: http://cr.openjdk.java.net/~hseigel/bug_8186092/webrev/

JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8186092

The change was tested with the JCK Lang and VM tests, the JTreg hotspot, 
java/io, java/lang, java/util, and other tests, the co-located NSK 
tests, JPRT, and with RBT tier2 - tier5 tests.

Thanks, Harold