Moved the changes-entry target to misc/developer.mk. To save some time,
that file is only included when PKG_DEVELOPER is defined.
Moved the build-defs-message target to misc/show.mk and renamed it to
show-build-defs, since almost all other *-message targets just print a
single line.
the internal/ directory to misc/, since it is not really internal to
pkgsrc.
Fixed the case where PKG_SKIP_REASON was not noticed by the bulk builds.
Added the NOT_FOR_UNPRIVILEGED and ONLY_FOR_UNPRIVILEGED variables.
