Print more information about class loaders in LinkageErrors. 
Since Java 9, class loaders have a name field. Report this if set.
Also report the parent class loader.

Changed messages:
=================

systemDictionary.cpp, 
---------------------------

SystemDictionary::check_constraints()
message 1:

before: 
loader (instance of PreemptingClassLoader): attempted duplicate class definition for name: "test/Foo"
loader (instance of PreemptingClassLoader): attempted duplicate class definition for name: "test/J"

after:
loader "<unnamed>" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) attempted duplicate class definition for test.Foo.
loader "DuplicateLE_Test_Loader" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) attempted duplicate class definition for test.Foo.
loader "DuplicateLE_Test_Loader_IF" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) attempted duplicate interface definition for test.J.

Improvements:
 * external names ('.' instead of '/')
 * more detailed loader description (name, class, parent)
 * distinguish classes, interfaces and abstract classes.

message 2:

before:
loader constraint violation: loader (instance of PreemptingClassLoader) previously initiated loading for a different type with name "test/D_ambgs"

after:
loader constraint violation: loader "<unnamed>" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) wants to load class test.D_ambgs. A different class with the same name was previously loaded by "app" (instance of jdk.internal.loader.ClassLoaders$AppClassLoader).

Improvements: 

 * external names ('.' instead of '/')
 * more detailed loader description (name, class, parent)
 * distinguish classes, interfaces and abstract classes.


klassVtable.cpp:
---------------------

message 3, klassVtable::update_inherited_vtable():

before:

loader constraint violation for class test/Task: when selecting overriding method "test.Task.m()Ltest/Foo;" the class loader (instance of PreemptingClassLoader) of the selected method's type test/Task, and the class loader (instance of jdk/internal/loader/ClassLoaders$AppClassLoader) for its super type test/J have different Class objects for the type test/Foo used in the signature

after:

loader constraint violation for class test.Task: when selecting overriding method test.Task.m()Ltest/Foo; the class loader "<unnamed>" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) of the selected method's type test.Task, and the class loader "app" (instance of jdk.internal.loader.ClassLoaders$AppClassLoader) for its super type test.J have different Class objects for the type test.Foo used in the signature

or

loader constraint violation for class test.Task: when selecting overriding method test.Task.m()Ltest/Foo; the class loader "VtableLdrCnstrnt_Test_Loader" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) of the selected method's type test.Task, and the class loader "app" (instance of jdk.internal.loader.ClassLoaders$AppClassLoader) for its super type test.J have different Class objects for the type test.Foo used in the signature

message 4, klassItable::initialize_itable_for_interface():

before:

loader constraint violation in interface itable initialization for class test/C: when selecting method "test.I.m()Ltest/Foo;" the class loader (instance of PreemptingClassLoader) for super interface test/I, and the class loader (instance of jdk/internal/loader/ClassLoaders$AppClassLoader) of the selected method's type, test/J have different Class objects for the type test/Foo used in the signature

after:

loader constraint violation in interface itable initialization for class test.C: when selecting method test.I.m()Ltest/Foo; the class loader "<unnamed>" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) for super interface test.I, and the class loader "app" (instance of jdk.internal.loader.ClassLoaders$AppClassLoader) of the selected method's type, test.J have different Class objects for the type test.Foo used in the signature"

or

loader constraint violation in interface itable initialization for class test.C: when selecting method test.I.m()Ltest/Foo; the class loader "ItableLdrCnstrnt_Test_Loader" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader) for super interface test.I, and the class loader "app" (instance of jdk.internal.loader.ClassLoaders$AppClassLoader) of the selected method's type, test.J have different Class objects for the type test.Foo used in the signature

Improvements: 

 * external names ('.' instead of '/')
 * more detailed loader description (name, class, parent)

 * Todo: external name in method signature?!

linkResolver.cpp:
---------------------

message 5  LinkResolver::check_method_loader_constraints():
message 6 LinkResolver::check_field_loader_constraints():

replaced parts mentioning the class loader:

before:

the class loader (instance of PreemptingClassLoader)

after:

the class loader "<unnamed>" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader)

or:

the class loader "My_Test_Loader" (instance of PreemptingClassLoader, child of "app" jdk.internal.loader.ClassLoaders$AppClassLoader)