RFR 8160551: assert(c == Bytecodes::_putfield) failed: must be putfield

[Coleen Phillimore]

Summary: Illegal bytecodes which are detected later hit this assert first.

Removed the asserts in the new code in the rewriter, and added a test 
that verifies that ICCE is thrown for the case in question.

Tested in progress with jck tests.

open webrev at http://cr.openjdk.java.net/~coleenp/8160551.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8160551

Zoltan: I borrowed your test directory name from your last review to 
also include my test.

Thanks,
Coleen