on platforms that need it.
XXX Right now, if the platform needs it, then it runs for every package.
XXX This needs to be fixed to only run for packages that install shared
XXX libraries.
* Move mk/plist/shlib-type to mk/scripts.
* Move definition of SHLIB_TYPE from mk/plist/plist.mk to bsd.pkg.mk.
* Move inclusion of bsd.pkginstall.mk below bsd.tools.mk so that it
can use SHLIB_TYPE. This is necessary because SHLIB_TYPE's value
is the result of evaluating a command, and the command needs "TOOL"
definitions provided by bsd.tools.mk.
