[foreign] RFR typedef with anonymous struct results in empty name in layout

[Sundararajan Athijegannathan]

Fixed Utils.java to use getIdentifier on Type to generate Layout NAME. 
Also added check to prevent empty name in LayoutResolver + tests.

http://cr.openjdk.java.net/~sundar/typedefanonstruct/webrev.00/index.html

Thanks,
-Sundar