patch 9.1.0418: Cannot move to previous/next rare word

Problem:  Cannot move to previous/next rare word
          (Colin Kennedy)
Solution: Add the ]r and [r motions (Christ van Willegen)

fixes: #14773
closes: #14780

Signed-off-by: Christ van Willegen - van Noort <github.com@vanwillegen-vannoort.nl>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/vim.h b/src/vim.h
index f359245..654e523 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1530,6 +1530,15 @@
 		  'z', 'Z', 'g'}
 
 /*
+ * Values for behaviour in spell_move_to
+ */
+typedef enum
+{
+    SMT_ALL = 0		    // Move to "all" words
+    , SMT_BAD		    // Move to "bad" words only
+    , SMT_RARE		    // Move to "rare" words only
+} smt_T;
+/*
  * Boolean constants
  */
 #ifndef TRUE