big: Improve int_bitfield_extract.

core/math/big/radix.odin

@@ -202,7 +202,7 @@ int_itoa_raw :: proc(a: ^Int, radix: i8, buffer: []u8, size := int(-1), zero_ter
 
 		for offset := 0; offset < count; offset += 4 {
 			bits_to_get := int(min(count - offset, shift));
-			if digit, err = extract_bits(a, offset, bits_to_get); err != .None {
+			if digit, err = int_bitfield_extract(a, offset, bits_to_get); err != .None {
 				return len(buffer) - available, .Invalid_Argument;
 			}
 			available -= 1;