disable explicitly overflow checks

tests/test/testi642.pp

@@ -1,3 +1,4 @@
+{$Q-} { this is necessary to avoid an overflow error below }
 {$mode objfpc}
 uses
    sysutils
@@ -1186,4 +1187,4 @@ begin
    writeln('                Int64 test successful');
    writeln('------------------------------------------------------');
    halt(0);
-end.
+end.