PHP 5.5 compatibility

After upgrading to PHP 5.5 I got a 'Bus Error 10' when including the module.

```
gdb php
(gdb) set args -m
(gdb) run

...

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x0000000100aed4e0
0x00000001001d1409 in _zend_hash_init ()
(gdb) bt
#0  0x00000001001d1409 in _zend_hash_init ()
#1  0x0000000100aea608 in zm_startup_jsonreader (type=<value temporarily unavailable, due to optimizations>, module_number=<value temporarily unavailable, due to optimizations>) at jsonreader.c:776
#2  0x00000001001cb78d in zend_startup_module_ex ()
#3  0x00000001001d273d in zend_hash_apply ()
#4  0x00000001001cbb33 in zend_startup_modules ()
#5  0x0000000100172e47 in php_module_startup ()
#6  0x000000010024df6f in php_cli_startup ()
#7  0x000000010024c4fe in main ()
```
Allocating the _jsonreader_prop_handlers_ HashTable solved this problem.