Log Message:
lang/pnet: Mask for all DragonFly platforms

It doesn't build on i386.  When gcconfig.h is modified to recognize x86_64
platform, it breaks in the Boehm garbage collector.  This is alpha-grade
software from GNU that hasn't had a release in over 4.5 years.  Frankly, I
don't know how this abandoned project deserves a spot in pkgsrc.