patch 9.0.0828: various typos

Problem:    Various typos.
Solution:   Correct typos. (closes #11432)
diff --git a/src/usercmd.c b/src/usercmd.c
index 0160ac1..9f16680 100644
--- a/src/usercmd.c
+++ b/src/usercmd.c
@@ -1420,7 +1420,7 @@
  * was added.  Return the number of bytes added.
  */
     size_t
-add_win_cmd_modifers(char_u *buf, cmdmod_T *cmod, int *multi_mods)
+add_win_cmd_modifiers(char_u *buf, cmdmod_T *cmod, int *multi_mods)
 {
     size_t result = 0;
 
@@ -1537,7 +1537,7 @@
 	}
     }
     // flags from cmod->cmod_split
-    result += add_win_cmd_modifers(buf, cmod, &multi_mods);
+    result += add_win_cmd_modifiers(buf, cmod, &multi_mods);
 
     if (quote && buf != NULL)
     {