stream_cdda: deprecate undocumented --cdda-span-{a,b} options

You probably wouldn't guess what this does from the name alone, but it
actually selects a range of tracks to play. It's slightly different than
using --start because it confines the range to just that track and you
cannot seek before it. The functionality is useful, but you can
accomplish exactly the same thing with --start and --end. Also the
implementation of the cdda option is weird because starting from a track
after 1 makes it impossible to seek before it. There's no reason to have
this when using the core option is simply better and works fine.

DOCS/interface-changes/cdda-span.txt

@@ -0,0 +1 @@
+deprecate `--cdda-span-a` and `--cdda-span-b`

stream/stream_cdda.c

@@ -76,8 +76,8 @@ const struct m_sub_options stream_cdda_conf = {
         {"overlap", OPT_INT(search_overlap), M_RANGE(0, 75)},
         {"toc-offset", OPT_INT(toc_offset)},
         {"skip", OPT_BOOL(skip)},
-        {"span-a", OPT_INT(span[0])},
-        {"span-b", OPT_INT(span[1])},
+        {"span-a", OPT_INT(span[0]), .deprecation_message = "--start=#N"},
+        {"span-b", OPT_INT(span[1]), .deprecation_message = "--end=#N"},
         {"cdtext", OPT_BOOL(cdtext)},
         {0}
     },