Avoid dead branches.

	* lib/subordinateio.c: Avoid dead branches.

Note: code is equivalent.
Add schematics with ranges to help reviews.

	* lib/subordinateio.c: Add schematics with ranges to help reviews.
Align coding style.

	* lib/subordinateio.c: Avoid implicit conversion of pointers and
	integers to booleans.
	* lib/subordinateio.c: Added brackets.