Description:
------------
I noticed that crc32() function result is represented differently on 32-bit and 64-bit platforms. The problem is whithin crc32.c file,

  unsigned int crc = ~0;

After actual crc32 calculations result is inverted and then casted to "long":

    RETVAL_LONG(~crc);

Proposed patch:

    RETVAL_LONG(~ (long) crc);

I tested it successfully on 64-bit linux and macosx, it works well.

Reproduce code:
---------------
<? echo crc32("platform independant") . "\n"; ?>


Expected result:
----------------
I expect to see value -858128794 both on 32-bit and 64-bit platform.


Actual result:
--------------
On 64-bit platform i see 3436838502
On 32-bit -858128794