Set sourcepkg to pkgname through run_template().

This removes the need for having to specify sourcepkg manually in
every package that will build subpkgs.

--HG--
extra : convert_revision : 383e4c467e84844d2f4f61ae5c5e07a5124e9cfb

shutils/tmpl_funcs.sh

@@ -205,6 +205,9 @@ set_tmpl_common_vars()
 
 	FILESDIR=${XBPS_TEMPLATESDIR}/${pkgname}/files
 	DESTDIR=${XBPS_DESTDIR}/${pkgname}-${version}
+	if [ -z "${sourcepkg}" ]; then
+		sourcepkg=${pkgname}
+	fi
 	SRCPKGDESTDIR=${XBPS_DESTDIR}/${sourcepkg}-${version}
 }