Code clean-up

Avoid to define MRB_INT16 and MRB_INT64 at the same time

Remove macro ANYARGS. It is not used in the core and bundled mrbgems. And it is possible to conflict an application's macro.

Merge branch 'suppress_intern' of https://github.com/crimsonwoods/mruby into crimsonwoods-suppress_intern

Clean up load.c

Fix-up string

Add error checks for small environments which pointer is less than 32bit. These code will be removed by optimizer if the target runs on 32bit or above.

fix the behavior of Module#ancestors

String#inspec & String#dump may raise an "arena overflow" error