modified to use irep->reps to reference child ireps.  preparation for
removing irep array from mrb_state.  note that instructions OP_LAMBDA,
OP_EXEC and OP_EPUSH are incompatible, and dumped mrb format has changed.
irep->pool not to be GCed
forgot to free irep->reps
create Proc object before releasing memory pool
wrong return value from read_lineno_record()
call_iseq will never be NULL
type check before pool scan
allow irep to be GCed
protect returning irep (in proc) from GC
Merge branch 'master' of github.com:mruby/mruby
check for corrupted mrb file data
cancel #1565 since it breaks mirb; instead add special treatment to heredocs
call codedump_all() from mirb if --verbose is set; close #1559