ref #4576 and ref #4947

* Need MRBAPI functions without `MRB_DISABLE_STDIO`:
  * mrbgems/mruby-bin-debugger
  * mrbgems/mruby-bin-mirb
  * mrbgems/mruby-bin-mrbc
  * mrbgems/mruby-bin-mruby
  * mrbgems/mruby-bin-strip
* Need `stdio.h`:
  * mrbgems/mruby-io
  * mrbgems/mruby-print
* Need `snprintf()` in `stdio.h`:
  * mrbgems/mruby-pack
  * mrbgems/mruby-sprintf