fix length check in read_section_debug()

Changed a variable declaration to top of block

Change supress to suppress

nextc(): always return an '\n' at end of input

fix #1564

removing irep array from mrb_state.  note that instructions OP_LAMBDA,
OP_EXEC and OP_EPUSH are incompatible, and dumped mrb format has changed.

mrbc: add line break for -c option, like other options