patch 9.0.0828: various typos

Problem:    Various typos.
Solution:   Correct typos. (closes #11432)
diff --git a/src/getchar.c b/src/getchar.c
index 5d0c994..57e184b 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -3942,7 +3942,7 @@
 		ga_concat(&line_ga, (char_u *)"<SNR>");
 	    else
 	    {
-		semsg(e_cmd_maping_must_not_include_str_key,
+		semsg(e_cmd_mapping_must_not_include_str_key,
 					       get_special_key_name(c1, cmod));
 		aborted = TRUE;
 	    }