add tests for fixed bugs

tests/lang/bug18872.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Bug #18872 (class constant used as default parameter)
+--FILE--
+<?php   
+class FooBar {   
+	const BIFF = 3;   
+}   
+   
+function foo($biff = FooBar::BIFF) {   
+	echo $biff . "\n";   
+}   
+   
+foo();   
+foo();   
+?>   
+--EXPECT--
+3
+3

tests/lang/bug23279.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Bug #23279 (exception handler stops after first function call)
+--FILE--
+<?php
+ob_start();
+set_exception_handler('redirect_on_error');
+echo "Hello World\n";
+throw new Exception;
+
+function redirect_on_error($e) {
+    ob_end_clean();
+    echo "Goodbye Cruel World\n";
+}
+?>
+--EXPECT--
+Goodbye Cruel World

tests/lang/bug23384.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Bug #23384 (use of class constants in statics)
+--FILE--
+<?php
+define('TEN', 10);
+class Foo {
+    const HUN = 100;
+    function test($x = Foo::HUN) {
+        static $arr2 = array(TEN => 'ten');
+        static $arr = array(Foo::HUN => 'ten');
+
+        print_r($arr);
+        print_r($arr2);
+        print_r($x);
+    }
+}
+
+Foo::test();   
+echo Foo::HUN."\n";
+?>
+--EXPECT--
+Array
+(
+    [100] => ten
+)
+Array
+(
+    [10] => ten
+)
+100100