[foreign] RFR jextract misses varargs flag for callback methods

[Sundararajan Athijegannathan]

jextract misses varargs flag for callbacks generated for C pointer to 
function with no arguments.

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

Thanks,
-Sundar