8227717: Give more helpful NullPointerException messages and add flag -XX:ShowCodeDetailsInExceptionMessages

[Lindenmaier, Goetz]

Hi Joe, 

I have changed the naming of the flag. 

What else should I add to the CSR? What is still missing?

> Not that the CSR covers a particular snapshot of a change so if there 
> are specific interfaces being modified, just referring to a JEP is not 
> sufficient since the JEP can be changed independently of the CSR. 
> In particular, a JEP can be modified after a CSR is approved.
Shouldn't the CSR cover what is submitted to the code base? I.e., 
the final state?  
What should I add to the text to cover this?  Do you want to know more
about the message texts that will be generated? Should I explain
in more detail which exceptions will get a message added?  Should
I describe the changes to NullPointerException.java?

Best regards,
  Goetz.