Remove array_pad's arbitrary length restriction

The error message was wrong; it *is* possible to use a larger length.
Furthermore, there is an arbitrary restriction on the new array's
length.
Fix both by checking the length against HT_MAX_SIZE.

Author: nielsdos

ext/standard/array.c

@@ -4224,13 +4224,14 @@ PHP_FUNCTION(array_pad)
 		Z_PARAM_ZVAL(pad_value)
 	ZEND_PARSE_PARAMETERS_END();
 
+	if (pad_size < Z_L(-HT_MAX_SIZE) || pad_size > Z_L(HT_MAX_SIZE)) {
+		zend_argument_value_error(2, "must not exceed the maximum allowed array size");
+		RETURN_THROWS();
+	}
+
 	/* Do some initial calculations */
 	input_size = zend_hash_num_elements(Z_ARRVAL_P(input));
 	pad_size_abs = ZEND_ABS(pad_size);
-	if (pad_size_abs < 0 || pad_size_abs - input_size > Z_L(1048576)) {
-		zend_argument_value_error(2, "must be less than or equal to 1048576");
-		RETURN_THROWS();
-	}
 
 	if (input_size >= pad_size_abs) {
 		/* Copy the original array */

ext/standard/tests/array/array_pad.phpt

@@ -84,4 +84,4 @@ array(4) {
   [3]=>
   float(2)
 }
-array_pad(): Argument #2 ($length) must be less than or equal to 1048576
+array_pad(): Argument #2 ($length) is too large because it results in a padding of 1999997 elements, which is larger than the allowed 1048576 elements