Convert watch file to format 5

debian/watch

@@ -1,4 +1,4 @@
-
-version=4
-opts=pgpsigurlmangle=s/$/.asc/ \
-    ftp://ftp.astron.com/pub/@PACKAGE@/@PACKAGE@-@ANY_VERSION@@ARCHIVE_EXT@
+Version: 5
+Source: ftp://ftp.astron.com/pub/@PACKAGE@/
+Matching-Pattern: @PACKAGE@-@ANY_VERSION@@ARCHIVE_EXT@
+Pgpsigurlmangle: s/$/.asc/