Introduce a boolean option.
If used, `int_var` is bitwise-ored with `mask`.
+`OPT_NEGBIT(short, long, &int_var, description, mask)`::
+ Introduce a boolean option.
+ If used, `int_var` is bitwise-anded with the inverted `mask`.
+
`OPT_SET_INT(short, long, &int_var, description, integer)`::
Introduce a boolean option.
If used, set `int_var` to `integer`.