Provide some vars for use in template's targets.

These new vars are DESTDIR (by default XBPS_DESTDIR/pkgname-version),
SRCPKGDESTDIR (XBPS_DESTDIR/sourcepkg-version) and FILESDIR
(XBPS_TEMPLATESDIR/pkgname/files).

This simplifies packages that used them.

--HG--
extra : convert_revision : 287ea7128cb5df19870ca7aff0a3b8f99a11d63a

templates/readline/template

@@ -38,9 +38,7 @@ pre_configure()
 
 post_install()
 {
-	local destdir=$XBPS_DESTDIR/$pkgname-$version
-
 	# Move shared libs into /lib.
-	mkdir -p $destdir/lib
-	mv $destdir/usr/lib/lib*.so* $destdir/lib
+	mkdir -p $DESTDIR/lib
+	mv $DESTDIR/usr/lib/lib*.so* $DESTDIR/lib
 }