Add initial default method support to Art

This commit starts the process of adding default methods and their
associated pieces to ART.

This adds full support for calling default methods using
invoke-interface and invoke-virtual on objects implementing the
interfaces. Verifier is changed to allow this when the runtime is
started with -Xexperimental:default-methods.

This also adds support for defining and calling static methods on
interface classes with invoke-static.

Directly calling overridden default methods using invoke-super is not
yet supported.

This adds 5 new run-tests for this functionality.

Bug: 24618811

Change-Id: I35ca800d99d3329348b277789b70ceeeba6e7f03
diff --git a/.gitignore b/.gitignore
index c4cf98b..4e806c6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 JIT_ART
+**/__pycache__/**