Add a regression test for #1152.

The test code is slightly changed in order not to depend on Array#map.
Merge branch 'master' into iij
Merge branch 'iij' of github.com:iij/mruby into iij
Merge branch 'iij' of github.com:iij/mruby into iij
Merge remote-tracking branch 'origin/pr-regression-1152' into iij