Treat abstract ctors the same, regardless of origin

Abstract ctor signatures should always be respected by all children,
independently of whether it comes from an interface or an abstract
class. Previously abstract ctor signatures (if they didn't come from
an interface) were only checked to one level of inheritance.

Author: nikic

Zend/tests/bug61970_2.phpt

@@ -15,4 +15,4 @@ class Baz extends Bar {
     protected function __construct(){}
 }
 --EXPECTF--
-Fatal error: Access level to Baz::__construct() must be public (as in class Bar) in %s on line 12
+Fatal error: Access level to Baz::__construct() must be public (as in class Foo) in %s on line 12

Zend/tests/constructor_abstract_grantparent.phpt

@@ -0,0 +1,18 @@
+--TEST--
+LSP checks are performed against an abstract constructor even if it is not a direct parent
+--FILE--
+<?php
+
+abstract class A {
+    abstract function __construct(X $x);
+}
+class B extends A {
+    function __construct(X $x) {}
+}
+class C extends B {
+    function __construct() {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Declaration of C::__construct() must be compatible with A::__construct(X $x) in %s on line 10

Zend/zend_inheritance.c

@@ -597,11 +597,11 @@ static void do_inheritance_check_on_method(zend_function *child, zend_function *
 					proto = parent;
 				}
 			} else if (proto) {
-				if (proto->common.scope->ce_flags & ZEND_ACC_INTERFACE) {
-					/* ctors only have a prototype if it comes from an interface */
-					/* and if that is the case, we want to check inheritance against it */
+				/* ctors only have a prototype if is abstract (or comes from an interface) */
+				/* and if that is the case, we want to check inheritance against it */
+				if (proto->common.fn_flags & ZEND_ACC_ABSTRACT) {
 					parent = proto;
-				} else if (!(proto->common.fn_flags & ZEND_ACC_ABSTRACT)) {
+				} else {
 					break;
 				}
 			} else {