Add new API `mrb_ary_resize`(mruby implementation of `rb_ary_resize`).
Remove unnecessary out of memory check in `ary_expand_capa`.
Since `mrb_realloc` raises when failed to allocate memory.
Print error instead of printing return value of report.
Use `mrb_print_error` to print exception instead of `mrb_p`.
Merge pull request #2449 from take-cheeze/mrb_ary_resize

Add new API `mrb_ary_resize`(mruby implementation of `rb_ary_resize`).
Merge pull request #2451 from take-cheeze/remove_mem_out_check

Remove unnecessary out of memory check in `ary_expand_capa`.
Clean up value.h and mrb_value boxing
rename SET_FIXNUM_VALUE to SET_INT_VALUE since it sets mrb_int value
rename word boxing functions
rename boxing_nix.h to boxing_no.h
Merge branch 'AE9RB-cleanup_mrb_value'
Merge branch 'master' of github.com:mruby/mruby
Merge pull request #2452 from take-cheeze/test_exc

Use `mrb_print_error` in test error handling.
remove unused return_value