Add support for binary, and octal number prefixes for INI settings

[Girgias]

This gives feature parity with INI setting values to use number prefixes in the same way PHP integers can accept them.

Future scope could be to have support for _ as sepators.

However, I'm not exactly sure how to tackle the negative number case. I don't know if it's sensible to move past the negative sign, compute the values as unsigned and then check for overflows before multiplying it by -1.

[arnaud-lb]

However, I'm not exactly sure how to tackle the negative number case. I don't know if it's sensible to move past the negative sign, compute the values as unsigned and then check for overflows before multiplying it by -1.

This seems to be nearly what strtol() does in the spec:

7.20.1.4
[...]
If the subject sequence has the expected form and the value of base is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value as given above. If the subject sequence begins with a minus sign, the value resulting from the conversion is negated

[Girgias]

Reopenned to trigger CI which didn't want to start because it was targeting the wrong branch

[arnaud-lb]

Looks good to me

[arnaud-lb]

Nit: We could simplify like this:

Suggested change

	if (digits[0] == '0' && !isdigit(digits[1])) {
	/* Value is just 0 */
	if ((digits+1) == str_end) {
	*errstr = NULL;
	return 0;
	}
	switch (digits[1]) {
	/* Multiplier suffixes */
	case 'g':
	case 'G':
	case 'm':
	case 'M':
	case 'k':
	case 'K':
	goto evaluation;
	case 'x':
	case 'X':
	base = 16;
	break;
	if (digits[0] == '0') {
	switch (digits[1]) {
	case 'x':
	case 'X':
	base = 16;
	digits += 2;
	break;

This allows to remove the special case for 0, and the multiplier suffix cases in the switch.

We can then remove the if (UNEXPECTED(digits == str_end)) { block (we can add a special case for "no digits after base prefix" in the "no valid leading digits" error bellow when base is not 0.)

[Girgias]

I've tried doing this and if I try to simplify it then I don't think I can have an error for invalid prefixes