Varargs records

[Brian Goetz]

As I was writing some tests for records, it occurs to me that we never 
explicitly discussed whether we should support _varargs_ records, such as:

     record StringBunch(String... strings) { }

The translation would be straightforward:
  - The type of the strings field is String[]
  - The return type of the strings accessor is String[]
  - The canonical constructor is of descriptor (String...) rather than 
(String[]), allowing varargs invocation of the constructor.
  - There would be the usual restriction that there can be only one 
varargs argument, and it must be last.

So this seems feasible.  Is this something we want?