Fixed build failure against php-5.6.0alpha3

Removed two unused functions.

```
...
/tmp/runkit/runkit_props.c:581:20: error: unused function 'php_runkit_dump_hashtable_keys' [-Werror,-Wunused-function]
static inline void php_runkit_dump_hashtable_keys(HashTable* ht) {
                   ^
1 error generated.
make: *** [runkit_props.lo] Error 1
$ php -v
PHP 5.6.0alpha3 (cli) (built: Mar 17 2014 23:15:45)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.6.0-dev, Copyright (c) 1998-2014 Zend Technologies
```