RFR (L, final): 8218626: Add detailed message to NullPointerException describing what is null.

[Lindenmaier, Goetz]

Hi Ralf,

> The test should not omit these two bytecodes because the current
> implementation is the same. This can change and it is not much additional code
> to add the two cases.
I implemented test cases for the missing invokes:

http://cr.openjdk.java.net/~goetz/wr19/8218628-exMsg-NPE/20-incremental/
http://cr.openjdk.java.net/~goetz/wr19/8218628-exMsg-NPE/20/

Best regards,
  Goetz.