Add new API mrb_ptr_as_string().
Remove *printf() that have "%p" format as possible. Use tomrb_ptr_as_string() instead.
Merge branch 'pr-add-mrb_ptr_as_string' of https://github.com/monaka/mruby into monaka-pr-add-mrb_ptr_as_string
rename mrb_ptr_as_string() to mrb_ptr_to_str()