Narrow scope of variable "i" in set_chars_option.
Narrow scope of variable "round" in set_chars_option
Move variable declaration in set_chars_option.

Move variable "entries" closer to (conditional) initialisation.
Narrow scope of variable "p" in set_chars_option.
Narrow scope of variable "s" in set_chars_option.
Narrow scope of variable "c1" in set_chars_option.
Narrow scope of variable "c2" in set_chars_option.
Better sizeof() style in set_chars_option.
Add optional curly braces in set_chars_option.
Better comment style for set_chars_option.
Post-increment style.
Move parsing logic in a separate function.

The parsing in set_chars_option uses a confusing logic. This
refactoring makes it appear more sequential, and allows for code
reuse.
Split 2-step in set_chars_option().