wrong size of filenames buffer
fix warning: "implicit conversion from enumeration type 'enum mrb_vtype' to different enumeration type 'enum irep_pool_type' [-Wenum-conversion]"
Merge pull request #1582 from takahashim/warning-enum-irep_pool_type

irep->pool[n].type should be IREP_TT_*, not MRB_TT_*
Merge branch 'master' of github.com:mruby/mruby
check upper callinfo to call ensure block; close #1579