General inline cache optimizations.
Enable inline caching for variant interface method calls.
Call methods for non-variant interface methods are now simple known-name call shims.
Signature inline cache tweaks
Test case updates
Don't cache methods of IPackedArray
Handle interface methods without signatures.
Handle binding failures for generic interface methods better.
Fix variant interface invocation corner case
Fix interface fallback methods.
Add comments to inline cache implementation.
Add more comments to IC implementation.
Generate switch statements instead of if statements in ICs.