patch 8.2.4565: no command line completion for :breakadd and :breakdel

Problem:    No command line completion for :breakadd and :breakdel.
Solution:   Add completion for :breakadd and :breakdel. (Yegappan Lakshmanan,
            closes #9950)

src/usercmd.c

@@ -90,6 +90,9 @@ static struct
     {EXPAND_TAGS_LISTFILES, "tag_listfiles"},
     {EXPAND_USER, "user"},
     {EXPAND_USER_VARS, "var"},
+#if defined(FEAT_EVAL)
+    {EXPAND_BREAKPOINT, "breakpoint"},
+#endif
     {0, NULL}
 };