This patch allows c1 to generate the optimized virtual call for invokeinterface
whose targets are the private interface methods.

Before JDK-823835, LambdaMetaFactory generates invokespecial in this case. Because the private
interface methods can not be overrided, c1 generates the optimized virtual call. After JDK-823835,
LambdaMetaFactory generates invokeinterface instead. C1 generates the regular virtual call because
it can not recognize the new pattern. If a multiple of subclasses all implement a same interface,
it is possible that they trash the IC stub using their own concrete klass in runtime.

Optimized virtual call uses relocInfo::opt_virtual_call_type(3), It will call VM
'resolve_opt_virtual_call_C' once and resolve the target to the VEP of the nmethod.
Therefore, this patch can prevent the callsite from trashing.

…alAccessError.

We need to checkcast for invokespecial even target->can_be_statically_bound() is false.
eg. https://github.com/openjdk/jdk/blob/master/test/jdk/java/lang/invoke/SpecialInterfaceCallI4.jasm#L33