that these directories will be conditionally removed (based on reference
counts), regardless of the value of PKG_CONFIG. Bump the PKGREVISION
for packages that were modified as a result.
have it be automatically included by bsd.pkg.mk if USE_PKGINSTALL is set
to "YES". This enforces the requirement that bsd.pkg.install.mk be
included at the end of a package Makefile. Idea suggested by Julio M.
Merino Vidal <jmmv at menta.net>.
