(pack200) assertion errors when processing lambda class files with IMethods

When running pack200 with assertion enabled assertions are fired, these
need to be investigated and fixed before GA.

% pack200 -J-Xmx1g -J-esa -J-ea -v output.jar.pack.gz rt.jar
not found: InterfaceMethodref=IMethod:java/util/streams/primitives/IntIterator.(Ljava/util/functions/Block;)V.forEach
Exception in thread "main" java.lang.AssertionError
        at com.sun.java.util.jar.pack.ConstantPool$Index.indexOf(ConstantPool.java:1102)
        at com.sun.java.util.jar.pack.BandStructure.encodeRef(BandStructure.java:1055)
        at com.sun.java.util.jar.pack.BandStructure$CPRefBand.encodeRefOrNull(BandStructure.java:1032)
        at com.sun.java.util.jar.pack.BandStructure$CPRefBand.putRef(BandStructure.java:1004)
        at com.sun.java.util.jar.pack.PackageWriter.writeByteCodes(PackageWriter.java:1620)
        at com.sun.java.util.jar.pack.PackageWriter.writeMembers(PackageWriter.java:1225)
        at com.sun.java.util.jar.pack.PackageWriter.writeClassesAndByteCodes(PackageWriter.java:1200)
        at com.sun.java.util.jar.pack.PackageWriter.write(PackageWriter.java:79)
        at com.sun.java.util.jar.pack.PackerImpl$DoPack.flushPackage(PackerImpl.java:594)
        at com.sun.java.util.jar.pack.PackerImpl$DoPack.flushAll(PackerImpl.java:548)
        at com.sun.java.util.jar.pack.PackerImpl$DoPack.run(PackerImpl.java:483)
        at com.sun.java.util.jar.pack.PackerImpl.pack(PackerImpl.java:98)
        at com.sun.java.util.jar.pack.Driver.main(Driver.java:313)