RFR: JDK-8209022: Missing checkcast when casting to type parameter bounded by intersection type

[Vicente Romero]

Please review fix for [1] at [2]. Javac was `forgetting` to coerce some 
expressions to the target type after erasure. Implying that there were 
missing checkcasts generated in the byte code.

Thanks,
Vicente

[1] https://bugs.openjdk.java.net/browse/JDK-8209022
[2]http://cr.openjdk.java.net/~vromero/8209022/webrev.00/jdk.dev.patch