Tag NLS aliases with pkgbase package

POSIX and en_US.US_ASCII are aliases (symlinks) to the C locale.  They were
not previously tagged with a pkgbase pacakge.  Add the tag so that they are
handled correctly on pkgbase-installed/updated systems.

[This is r356990 reapplied with a corrected commit message.]

Discussed with:	manu

etc/Makefile

@@ -164,7 +164,8 @@ distrib-dirs: ${MTREES:N/*} distrib-cleanup .PHONY
 .endif
 .if ${MK_NLS} != "no"
 .for alias nls in ${NLS_ALIASES}
-	${INSTALL_SYMLINK} "${nls}" "${DESTDIR}${SHAREDIR}/nls/${alias}"
+	${INSTALL_SYMLINK} -T "package=utilities" \
+	    "${nls}" "${DESTDIR}${SHAREDIR}/nls/${alias}"
 .endfor
 .endif