patch 8.0.0356: leaking memory when setting 'ttytype'

Problem:    Leaking memory when setting 'ttytype'.
Solution:   Get free_oldval from the right option entry.

src/option.c

@@ -5936,6 +5936,7 @@ did_set_string_option(
 	    /* Both 'term' and 'ttytype' point to T_NAME, only set the
 	     * P_ALLOCED flag on 'term'. */
 	    opt_idx = findoption((char_u *)"term");
+	    free_oldval = (options[opt_idx].flags & P_ALLOCED);
 	}
     }
 

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    356,
 /**/
     355,
 /**/