no checking of numerical parameter values

[dnalor]

given

		ARGPARSE_OPTION(INT, 'n', "--number", &opt_n, "int nr"),

running the following will "successfully" result in opt_n=0

./prg -n WTF
./prg -n " "
./prg -n \?

same issue for FLOAT

cause: YOLO-style use of strtol / strtof:
in update_value:

       res = string ? strtol(value, NULL, 0) : *(int *)value;

and

        *(float *)arg->value_ = string ? strtof(value, NULL) : *(float *)value;

see strtol(3) and strtod(3) on why