At one point bsd.port.mk put out erroneous PLIST-auto, with @cwd, @pkgname,
and @pkgdep lines.
These are actually added by make package, and shouldn't usually be put
inside the PLIST, as this is extra information to update.
I left a few @cwd in, mainly for the perl modules, which want to live under
/usr to work.
Porters: please make sure you use bsd.port.mk 1.75 or later when
updating ports. That version of the makefile adds all sums. Previous
versions of the makefile will still work for people installing ports.