patch 8.2.1577: Vim9: hasmapto()/mapcheck()/maparg() do nottake "true" arg

Problem:    Vim9: hasmapto(), mapcheck() and maparg() do not take "true" as
            argument.
Solution:   Use tv_get_bool(). (closes #6822, closes #6824)

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1577,
 /**/
     1576,
 /**/