patch 9.0.0828: various typos

Problem:    Various typos.
Solution:   Correct typos. (closes #11432)
diff --git a/src/eval.c b/src/eval.c
index 062fab0..b815113 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3269,7 +3269,7 @@
 	    if (var2.v_type != VAR_NUMBER)
 		emsg(_(e_bitshift_ops_must_be_number));
 	    else
-		emsg(_(e_bitshift_ops_must_be_postive));
+		emsg(_(e_bitshift_ops_must_be_positive));
 	    clear_tv(rettv);
 	    clear_tv(&var2);
 	    return FAIL;