vim-patch:9.0.1330: handling new value of an option has a long "else if" chain

Problem:    Handling new value of an option has a long "else if" chain.
Solution:   Use a function pointer. (Yegappan Lakshmanan, closes vim/vim#12015)

af93691b53

src/nvim/spellfile.c

@@ -1851,7 +1851,7 @@ static void spell_reload_one(char *fname, bool added_word)
   // When "zg" was used and the file wasn't loaded yet, should redo
   // 'spelllang' to load it now.
   if (added_word && !didit) {
-    did_set_spelllang(curwin);
+    parse_spelllang(curwin);
   }
 }