Description:
------------
The new DatePeriod class seems to crash PHP in different ways. 







Reproduce code:
---------------
Crash #1: invalid argument: arg #1 should be DateTime

<?php

$dp = new DatePeriod('2D');

?>

Crash #2: valid argument (i think):
<?php

$begin = new DateTime();
$interval = DateInterval::createFromDateString("1 day");

$dp = new DatePeriod($begin, $interval, 10);

?>




Expected result:
----------------
$dp to be an instance of DatePeriod. Possibly an exception for giving it 
an unknown argument ( not sure what the syntax of the argument should be 
).






Actual result:
--------------
Crashes in both cases:

Crash #1: invalid argument:
-----------------------------------------
(gdb) run DatePeriod.php
Starting program: /Users/mathieu/programs/php/bin/php DatePeriod.php
Reading symbols for shared libraries ++++++.. done

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x000000a0
0x00050d45 in timelib_update_ts ()
(gdb) bt
#0  0x00050d45 in timelib_update_ts ()
#1  0x000317f9 in zim_DatePeriod___construct ()
#2  0x00295bec in zend_do_fcall_common_helper_SPEC ()
#3  0x00294885 in execute ()
#4  0x00272276 in zend_execute_scripts ()
#5  0x00219114 in php_execute_script ()
#6  0x0031d10e in main ()
------------------------------------------

Crash #2: valid argument:
------------------------------------------
(gdb) run DatePeriod.php 
Starting program: /Users/mathieu/programs/php/bin/php DatePeriod.php
Reading symbols for shared libraries ++++++.. done

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x00000000
0x00052649 in timelib_strtointerval ()
(gdb) bt
#0  0x00052649 in timelib_strtointerval ()
#1  0x0003177e in zim_DatePeriod___construct ()
#2  0x00295bec in zend_do_fcall_common_helper_SPEC ()
#3  0x00294885 in execute ()
#4  0x00272276 in zend_execute_scripts ()
#5  0x00219114 in php_execute_script ()
#6  0x0031d10e in main ()
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