Fix Closure::call() on internal method closure

In this case we should use the original internal handler. Otherwise
the trampoline will attempt to free the closure, but the function
being used is not actually part of a closure anymore.

Author: nikic

Zend/tests/closure_call_internal.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Closure::call() on internal method
+--FILE--
+<?php
+
+var_dump(Closure::fromCallable([new DateTime(), 'getTimestamp'])->call(new DateTime('@123')));
+
+?>
+--EXPECT--
+int(123)

Zend/zend_closures.c

@@ -152,6 +152,9 @@ ZEND_METHOD(Closure, call)
 		my_function.common.fn_flags &= ~ZEND_ACC_CLOSURE;
 		/* use scope of passed object */
 		my_function.common.scope = Z_OBJCE_P(newthis);
+		if (closure->func.type == ZEND_INTERNAL_FUNCTION) {
+			my_function.internal_function.handler = closure->orig_internal_handler;
+		}
 		fci_cache.function_handler = &my_function;
 
 		/* Runtime cache relies on bound scope to be immutable, hence we need a separate rt cache in case scope changed */