fix 3a4c8e2

unfortunately the previouse commit is incorrect, which still concate the
keywords, but like this:

      method='"end\nb"' (201)
Merge pull request #1553 from Fleurer/fix1550-cont

fix 3a4c8e2
restore context status to RUNNING on automatic yield at the end of the block; fix #1555
Merge branch 'master' of github.com:mruby/mruby
add mrb_ary_modify(mrb,a); you have to ensure mrb_value a to be an array; ref #1554