Replace Tab with spaces in src/parse.y

Use mrb_calloc if you want zero cleard buffers.

Add tests for Modules

Improvement of Module#include.

Optimize range check.

Brush up mrb_calloc().

- Add some methods: append_features, included_methods and included.
- Modify Module#include to call append_features and included.

Clean up dump.c

dump_irep_record(): Set error code in case dump failed.