Add @intlog2 for Floored CT log-base2 (#2355)

* Add `@intlog2` for Floored CT log-base2
---------

Co-authored-by: Christoffer Lerno <christoffer@aegik.com>

lib/std/math/math.c3

@@ -344,6 +344,23 @@ macro log(x, base)
 *>
 macro log2(x) => $$log2(values::promote_int(x));
 
+<*
+ @require values::@is_int($x) : `The input value must be an integer.`
+ @require $x >= 0 : `The input value must be a positive integer.`
+ @return `A floored base-2 log of an input integer value.`
+*>
+macro @intlog2($x)
+{
+	$if $x <= 1:
+		return 0;
+	$endif
+
+	$typeof($x) $z = 0;
+	$for var $y = $x; $y > 0; $y >>= 1, ++$z: $endfor
+
+	return $z - 1;
+}
+
 <*
  @require values::@is_promotable_to_floatlike(x) : `The input must be a number or a float vector`
 *>